|“||No one stands on the top of the world. Not you, not me, not even gods. But the unbearable vacancy of the throne in the sky is over. From now on... I will be sitting on it.||„|
|~ Aizen to Ukitake|
Sosuke Aizen is the former captain of the 5th Division in the Gotei 13, before he leaves Soul Society and the original main antagonist of Bleach.
PastAizen took part in the research on the Hōgyoku long before Kisuke Urahara did, sacrificing various Soul Reapers to create his own Hōgyoku. At one point, Aizen endangered Rangiku Matsumoto in the development of his Hōgyoku, which caught the attention of Gin Ichimaru. Originally, Aizen was the lieutenant of Squad 5 under Shinji Hirako. But feeling that Aizen was not who he claims to be, Shinji kept a close eye on his aide. After Kisuke was made the new captain of Squad 12, Aizen recruited Gin after watching him kill Squad 5's 3rd seat. 91 years prior to the series events, Aizen set up a scheme to have his other accomplice Kaname Tōsen lure out ideal test subjects with strange string of deaths in the Rukongai to test the Hōgyoku on in order to create Soul Reaper/Hollow hybrids.
By the time Shinji arrived, many of the gathered Shinigami were undergoing a Hollowification process. Revealing himself as the mastermind, Aizen revealed to his captain that he played on his distrust for him by using his Kyoka Suigetsu to create an illusionary double to fool him, which Shinji might have noticed if he'd tried to become close to Aizen. Subjecting Shinji to the Hollowification process, Aizen stated that Shinji had himself to blame for the turn of events. As Aizen prepared to kill his captain, Kisuke and Tessai Tsukabishi arrived with Aizen admitting he was responsible. However Aizen refused to go into the details of how he’d turned Shinji and the others into the beings later called Visoreds as he and his aides took their leave after Aizen managed to easily stop a Kidō spell from Tessai.Soon after the incident, Aizen became the new captain of Squad 5 with Gin as his lieutenant, before he becomes Squad 3 captain while Tōsen eventually became captain of Squad 9. Regardless, Aizen continuing his Hollow experimentation. While he was testing a new breed of Menos Hollow able to hide their spiritual energy, a group of Soul Reaper Academy first-years caught Aizen’s attention, Momo Hinamori, Izuru Kira, and Renji Abarai. He saw great potential in them and had them all put in his division. Eventually Momo and Izuru became Aizen and Gin’s lieutenants, while Renji was too rebellious and ended up in the Squad 11 and later Squad 6. Aizen also created the Soul Reaper assimilating Hollow Metastacia whose actions left a deep impression on Rukia Kuchiki. At one point, Aizen and his aides to Hueco Mundo to recruit the Hollows living there to become his Arrancars with the strongest to become his Espadas. Two such recruits are Baraggan Louisenbairn, after humiliating him into accepting his proposal, and Tier Harribel, by playing on her ideals.
Approximately 20 years before the events in Bleach, Aizen created a Hollow from a Soul Reaper and named the monster White before sicking his creation on Karakura town. Though he disabled Soul Reaper captain Isshin Shiba to put White at an advantage, the intervention of a Quincy named Masaki Kurosaki was able to kill it. However, noting that White transferred itself into Masaki, Aizen deemed the experiment isn't quite over. It was only five years after that event that Aizen learned of Ichigo Kurosaki’s birth, deeming him a ideal specimen to evolve into his full potential. To that end, Aizen arranged for Rukia to be stationed in Karakura Town so she could make Ichigo a Soul Reaper while pitting the youth against various Hollows he sends to test him.
Soul Society arcAfter arranging for Rukia Kuchiki to be arrested by the Gotei 13 and brought back with the Hogyoku in her body, Aizen then began his master plan. He first killed all the members of the Central 46, allowing him to move up Rukia’s execution date. Aizen began sowing suspicion throughout the Gotei 13, particularly against Gin. He then used his Zanpakuto’s power to make everyone believe he was dead with Gin being the prime suspect as his murderer. Aizen also lead Momo to believe that captain Toshiro Hitsugaya, her childhood friend, was his murderer to remove her from the picture. As things were getting more and more suspicious, the Gotei 13 began splitting into factions and fighting amongst themselves while Gin continued with Aizen’s plan. Aizen hid in the SRDI watched Ichigo possessed by Hollow Ichigo battling Byakuya with use of a camera disguised as a fly. Gin approached him, asking if Ichigo had undergone Hollowfication, but Ichigo regained control of his body, much to Gin’s disappointment. Aizen just told him there was nothing to worry about and everything was going according to plan. Aizen then revealed himself as a traitor, almost killing Momo and taking down Hitsugaya. However captain Retsu Unohana and her lieutenant, Isane Kotetsu, showed up, having figured out that there was something off about Aizen’s “corpse”. He revealed the true abilities of his Zanpakuto, as well as that Tōsen was working with him as well. Aizen and Gin then teleported to Sokyoku Hill, where Tōsen had Renji and Rukia waiting. Aizen told Renji to give up Rukia, but he refused and the captain noted how stubborn he was, saying that he could hold on to Rukia, but he’d have to leave his arms behind. Aizen then attacked Renji, but he managed to dodge, though his right arm was wounded. The rogue captain said he was pleased by Renji’s improved skills since he used to be in his division. Aizen then told the lieutenant that he didn’t want things to get more difficult, since he found it hard to hold back his full power and he didn’t want to see a former subordinate die. Renji then asked Aizen why he mortally wounded Momo, but he replied that he’d done so out of compassion, since she’d been trained to be unable to live without him. Renji said that Aizen was not the captain he’d known, but the rogue captain said that no one had known who he really was. The lieutenant attacked with his Zanpakuto’s Shikai, only for Aizen to block it easily and slash it apart with his sword, badly wounded Renji at the same time. The lieutenant still refused to let him take Rukia so Aizen tried to finish him off, but Ichigo intervened. Ichigo and Renji tried to work together to take down Aizen, but he easily stopped them and practically cut Ichigo in two. He began taking Rukia away, telling Ichigo his plans, but captain Sajin Komamura arrived on the scene and tried to stop him. However Aizen used a powerful Kido spell to severely wound Komamura, before taking the Hogyoku out of Rukia’s body. She managed to survive, much to Aizen’s surprise and he told Gin to kill her as he made to leave. However Byakuya Kuchiki shielded her from the attack and Aizen prepared to kill her himself. But Yoruichi Shihoin and Sui-Feng arrived with Sui-Feng threatening to kill him if he moved at all. Aizen said that it was nostalgic to see Yoruichi again, but three of the Seireitei’s gatekeepers arrived, having joined Aizen, and the rogue captain said that not even her and Sui-Feng could pursue him while they were fighting the gatekeepers. However Kukaku Shiba and Jidanbo Ikkanzaka arrived to help fight and Gin was restrained by Rangiku. Every capable captain and lieutenant arrived on the scene, surrounding Aizen and his cohorts. However Aizen smiled, saying it was time, and Yoruichi and Sui-Feng quickly moved away. A large beam of light suddenly surrounded Aizen, Gin, and Tōsen as a pack of Gillian Hollow's appeared in a hole in the sky. Captain-Commander Yamamoto called off the others, explaining that the light around the trio was a Negación, a separate world created by Gillians to rescue one of their number and bring them back to Hueco Mundo. Aizen, after removing his glasses and changing his hair, declared that he was going to stand atop the world as a god, before saying goodbye to his former comrades and telling Ichigo that for a human, he was rather interesting.
Arrancar arcSoon after, Aizen met the naturally born Arrancar Coyote Starrk and his off shoot Lilynette Gingerbuck, talking them into following him due to his tolerance to their spirit pressure. Aizen later sent Grand Fisher and two-pseudo Arrancar to the human world, which were killed by Isshin Kurosaki and Ryuken Ishida. Isshin and Urahara speculated that they had been sent by Aizen to get information on Ichigo. Eventually, Aizen sent Ulquiorra Cifer and Yammy Llargo to get him a report on how strong Ichigo had become. They returned to a meeting of Aizen and numerous other Arrancar, where Ulquiorra crushed his left eye, showing his master and comrades what he’d seen. Aizen looked on as Grimmjow Jaegerjaquez questioned leaving Ichigo alive and Ulquiorra explained that Ichigo wasn’t a threat, Aizen was only concerned with his growth rate.
Grimmjow and his Fracción invaded Karakura Town to kill Ichigo and his friends, but Tōsen went and brought the 6th Espada back. Aizen decided not to punish Grimmjow, saying he’d dismiss his actions as an overzealous display of loyalty. However Tōsen took action himself, cutting off the 6th Espada’s arm and incinerating it with a Kido spell. Later, Aizen, having analyzed Orihime Inoue’s powers, ordered Ulquiorra to organize another invasion of Karakura Town, though he insisted that Grimmjow go along. While Grimmjow, Yammy, Luppi Antenor, and Wonderweiss Margela kept Ichigo and the Shinigami occupied, Ulquoirra succeeded in making Orihime join them. He brought her to Aizen, who had her demonstrate her powers by regenerating Grimmjow’s arm. Aizen explained to his Arrancar that Orihime’s power allowed her to reject any kind of phenomena.After Ichigo, along with Uryu Ishida and Yasutora “Chad” Sado arrived in Hueco Mundo to rescue Orihime, Aizen called a meeting of the Espada. After giving everyone a cup of tea, he told them about the trio’s arrival. The Espada were quick to dismiss them as no threat, but Aizen warned them that Ichigo and his friends were not to be underestimated, telling them how they’d taken on the entire Gotei 13. Grimmjow got up to leave, saying he was going to go wipe the three out. However Aizen told him to stop and finally used his spiritual energy to subdue Grimmjow. He then told the Espada to wait in their quarters and while they shouldn’t be overconfident, there was no need to be afraid of Ichigo and his friends. Aizen then said that together, they were unstoppable.
Later, Aizen had Loly Aivirrne and Menoly Mallia bring Orihime to his throne room, where he showed her the Hogyoku. He told her that this act was supposed to show that he trusted her and asked her to heal some slight deterioration the Hogyoku suffered due to its constant use.
Hueco Mundo arcAfter Ichigo and his friends managed to reach Las Noches, a messenger told Aizen that Dordoni Alessandro Del Socaccio was dead, which didn’t surprise him. However he noted that the fact that Ichigo had struggled against him did. Aizen went on to say that the messenger had failed to mention that the Exequias had finished off Dordoni and demanded to know who sent them after the Privaron Espada. Szayel Aporro Granz appeared, revealing that it was him, and begged for Aizen to forgive him. The former captain told him he didn’t mind, telling Szayel to make more thorough reports, before asking him if the information he got from Dordoni would really help his research.
Szayel said it would, before leaving and Gin asked Aizen if he was enjoying himself despite his forces getting beaten. The former captain admitted that he was feeling an emotion much like enjoyment. After half of the Espada were killed fighting Ichigo, his friends, and the newly arrived Shinigami captains, Aizen had Starrk bring Orihime to him. He told her to wait there while he and his comrades went to destroy Karakura Town, so as to create the Oken, a key needed to reach the Spirit King and requiring 100,000 souls to create. Aizen had Tōsen cast the Tenteikura spell, allowing him to reveal to Ichigo and the others the real reason he’d captured Orihime.
Fake Karakura Town arcBy taking her to Las Noches, Ichigo and his friends would’ve gone to her rescue, thus losing the Soul Society a strong ally. Now Aizen and his forces could attack Karakura Town easily and he left for Karakura Town with Gin, Tōsen, Starrk, Lilynette, Baraggan, Tier Harribel, and their Fracción, sealing the portals there so Ichigo and his comrades could not follow.
Upon arriving however, Aizen found the other captains and lieutenants of the Gotei 13 waiting for him and Karakura Town swapped with a copy. Aizen just said that he’d have go to the Soul Society to destroy the real Karakura Town after he and his forces dealt with the Gotei 13. But before Aizen could do anything, he was trapped in a fire prison by Yamamoto along with Gin and Tōsen. He was undeterred, saying that his Espada would be able to deal with the Shinigami. As the battle went on, Momo eventually arrived to help Rangiku and Aizen was intrigued when he sensed her, having believed that he’d succeeded in killing her.Gin asked him if something was wrong, but Aizen said her presence wouldn’t change anything. Eventually Wonderweiss arrived with the creature, Fūrā, which used its breath to dispel the fire prison around Aizen and his cohorts. This quickly caught the attention of the Soul Society and Izuru Kira even feared that the Soul Society was going to lose. However the Visored arrived to help and Aizen was confronted by Shinji, who tried to slash at him, but Tōsen took him on instead. As the battle continued, Baraggan, about to die from his Respira being turned against him, threw his Gran Caida axe at Aizen in an attempt to kill him for usurping him in the past. However the Respira dissolved the axe before it could reach Aizen and the same quickly happened to Baraggan himself. Aizen continued to watch the fight as Starrk was struck down and Harribel fought Hiyori, Lisa Yadomaru, and Hitsugaya. Finally he stepped between Gin and Shinji’s fight, saying it was time to end the fight. Aizen suddenly slashed Harribel across the torso, telling her that she didn’t’ seem strong enough to fight for him, and told Gin and Tōsen it was to time to leave. Aizen then told Harribel that despite all the trouble he went through to gather the Espada, he was more powerful than all of them. The 3rd Espada stabbed Aizen, but he didn’t react and said that it was such a pain to deal with her. Harribel realized that she’d attacked an illusion as Aizen stabbed her in the back.
He said that he’d never again let her raise her blade against him and let her fall to the ground. Aizen told the Gotei 13 and Visored to all come at him and Shinji warned the other Visored not to attack him recklessly. However Aizen taunted them by saying that they’d died 100 years ago so they shouldn’t be afraid. This managed to make Hiyori angrily charge at him, only to get slashed in half by Gin Ichimaru. Shinji went to her side and stared angrily at Aizen, who noted that there was finally some life in his eyes. He then told his former captain to come and face him and Shinji engaged Aizen, telling the others to stay back and wait for Ichigo. Aizen asked why he had so much faith in Ichigo and Shinji said that he didn’t expect him to understand since he had no faith in his servants. Aizen said only the weak relied on others and Shinji asked how he could say that with all the minions under his command, since he must have asked them to trust him. Aizen replied that he never did, he told them to not trust anyone, even him, but there weren’t many people with the strength to do so.
Aizen said that all creatures wanted to believe in something bigger than them, unable to live without blind obedience. To escape the pressure of that trust, they look for someone higher than themselves, so they look for someone stronger than them. That was how kings and gods were born. Aizen went on to say that all served him and they would now witness the power of the god his followers believed in. Shinji drew his sword and asked Aizen if he was scared, but he said nothing and Shinji said there was no point in ignoring him. He repeated what Aizen said about Shinji not being open when he betrayed him.The Visored went on to say that because of that, Aizen didn’t have any idea what abilities his Zanpakuto had. Shinji went on to tell his former lieutenant that if he thought his Zanpakuto was the only one able to control people’s senses he was wrong and released his Zanpakuto. Aizen noted that his Zanpakuto’s Shikai had an interesting shape and Shinji activated the ability of his Zanpakuto, creating a world where all of Aizen’s senses were reversed. Shinji managed to land an attack on him, but his former lieutenant managed to figure out how the ability worked and slashed Shinji across the back, calling his power child’s play. However Ichigo arrived on the scene, moving right in to attack Aizen, but he managed to block with a barrier. Aizen taunted Ichigo, avoiding his attacks, and making him lose his resolve. However Komamura told Ichigo not to be disheartened and he, along with the other Shinigami and Visored, helped Ichigo fight Aizen while making sure he didn’t fall under the influence of Kyoka Suigetsu. Hitsugaya engaged him, but couldn’t land a single attack on Aizen, who continued to enrage him. The former captain was suddenly attacked by Komamura and Love Aikawa, but managed to protect himself. Komamura released his Bankai, only for Aizen to cut off its arm, doing the same to Komamura. Rojuro “Rose” Otoribashi tried to attack next, only for Aizen to grab his Zanpakuto, allowing him to pull the Visored in and cut him down. He proceeded to take down all the other Visored, calling them “Pseudo Arrancar”. Aizen continued to fight off the captains, until Hitsugaya managed to stab him through the chest with help from Shinji’s Zanpakuto power. However the Aizen he stabbed was an illusion and he’d swapped places with Momo, ending up on the ground next to Kira and Tetsuzaemon Iba. Ichigo, able to see through the hypnosis, helped the captains realize what happened and Kira and Tetsuzaemon tried to stop Aizen, only to get cut down. Shinji demanded to know when he created the illusion, but Aizen asked when they thought he wasn’t using the power of his Zanpakuto. Hitsugaya charged at Aizen in rage, despite Shunsui warning him not to, and the former captain noted that all of them were completely open, cutting down Hitsugaya, Shunsui, Sui-Feng, and Shinji. Yamamoto attacked Aizen, who said that the Gotei 13 would fall with him and managed to stab him in the chest. However Yamamoto, knowing that this was the real Aizen, grabbed him and pulled him in so as to use is Ennetsu Jigoku technique, which would incinerate everything in the area. However Wonderweiss showed up in Reusrrección form and attacked Yamamoto, absorbing all the fire of his Zanpakuto. Aizen explained that he knew he couldn’t beat Yamamoto alone and Wonderweiss had been designed solely to negate the powers of his Zanpakuto, Ryujin Jakka. However Yamamoto easily changed to hand-to-hand combat and destroyed Wonderweiss. But Aizen revealed that Ryujin Jakka’s flames had been stored inside the Arrancar and Yamamoto leapt onto his body to contain them as the flames exploded out of Wonderweiss’ remains. However as Aizen approached Yamamoto, he used a Kido spell, Itto Kaso, that badly damaged his arm and Ichigo attacked him, managing to knock him into a building. Ichigo managed to injure Aizen, but the wound quickly closed and Aizen revealed that the Hogyoku had been implanted in his torso, thus it had healed him. The former captain also noted that Ichigo had grown well, exactly according to his plans. He explained that Ichigo was the perfect test subject for his research and all the times when he had grown greatly in power had been just as Aizen desired.
Ichigo said he had to be lying, given what he had said back in the Soul Society, but Aizen said that was when he was lying. However Isshin, Ichigo’s father, arrived on the scene, saying that Aizen had said too much, before he sent Ichigo into the distance. Aizen noted that was a smart decision, before asking Gin how long he’d been just watching, though Gin replied that he hadn’t seen an opportunity to join in. Isshin engaged Aizen and eventually he noticed that Aizen was starting to tire. The former captain said that he’d reach the limits of his Shinigami abilities and the Hogyoku was beginning to understand his desires. Aizen explained the Hogyoku had its own will, which he found out only after taking it as his own. He said that the Hogyoku’s true power was not its ability to remove the boundary between Shinigami and Hollows, it could capture and materialize the hearts of those around it.
Aizen stated that it had brought about the miracles around Ichigo, Rukia, and Urahara and said that Urahara misunderstood the Hogyoku’s nature, because he had wanted to break down the barrier between Shinigami and Hollows. Aizen said Ichigo, Chad, and Orihime gained their powers thanks to the Hogyoku and was about to continue explaining when Gin smashed Ichigo into a building. While Ichigo talked with Isshin, Gin asked Aizen if he interrupted his speech, but his master said he’d finished as the Hogyoku began enveloping his body, saying that it deserved its name.However Urahara suddenly attacked him from behind and Aizen welcomed him to the fight. Urahara said that it had been a long time since they last saw each other and noted that Aizen had taken quite the interesting form. He replied that the midpoint of evolution was never pleasant looking, but Urahara pointed out that no one had called his form ugly. He noted that Aizen had fused with the Hogyoku, but he said that he had subjugated the Hogyoku, the thing Urahara failed to do. Urahara said that it was true he hadn’t mastered it in the past and Aizen said he must be unwilling to accept defeat. He proceeded to stab what he thought was Urahara, saying he’d forever the lost the chance to control the Hogyoku, but the Urahara he stabbed burst and the real Urahara appeared, binding him with a Kido spell. Aizen said he remembered the former captain’s Gigai trick from Yammy’s report and admitted that he had let his guard down, thinking Urahara would never use such a petty tactic. Aizen asked him what he was going to do now that he was constricted with a “meager” spell. Urahara asked what it would take to make the spell more than “meager” and used a barrage of binding spells on Aizen. Urahara then used another offensive Kido spell against Aizen, generating a large explosion. He said that Aizen truly had lowered his guard thanks to his new power and Aizen began attacking him, saying the Hogyoku made him unstoppable, so he didn’t need to avoid attacks. Urahara said he wasn’t taking about avoiding the Kido spells, he meant that previously, Aizen would never come in contact with him twice without any plan. Handcuffs made of spiritual energy suddenly appeared on Aizen’s arms and Urahara explained that it was a seal that would incinerate his spiritual energy from the inside out, while Aizen was surrounded by a pillar of light. However he emerged from the resulting explosion, unscathed with the Hogyoku having transformed him. Urahara, Isshin, and Yoruichi all engaged Aizen, managing to crack his new form, but he also managed to destroy some of Yoruichi’s armor. He asked if that was all they could throw at him and noted that Yoruichi’s armor must have been special if she had survived his attack, thus he was going to destroy that first. Aizen succeeded in destroying more of Yoruichi’s armor and watched as she and Urahara argued. Urahara said Aizen was showing interest again and he explained that he still found him interesting, since he was the only person in the Soul Society that was more intelligent than him. Urahara, Yoruichi, and Isshin attacked Aizen again, but only succeeded in cracking his form again and he finally struck them all down. He left with Gin for the Soul Society as his chrysalis form fell away to reveal his transformed face. As they headed through the Dangai, Aizen encountered the Kōtotsu and managed to do the impossible: destroy it. Once in Karakura Town, Aizen killed a man with merely his spiritual energy and came across Tatsuki Arisawa and Keigo Asano. Don Kanonji appeared to stop him, but he could do little to Aizen. Rangiku arrived and Gin took her away to deal with ehr himself, while Aizen hunted down the humans in a game of cat and mouse. As the former captain moved in on Ichigo’s friends, Zennosuke Kurumadani arrive and used his Zanpakuto’s Shikai to bury him in rubble. However this did little to deter Aizen, but Ichigo’s friends ran away as Gin returned to the former captain’s side. When he stated he killed Rangiku Aizen noted he was surprise, Aizen stated that he intended to kill Ichigo's friends before carrying out his intent. However, grabbing Aizen's sword, Gin revealed his Bankai and impaled Aizen through the chest. Gin reminded Aizen that he’d told him how to avoid being affected by his Zanpakutō, touching its blade while it was unreleased. Aizen said that he always knew Gin would turn on him, but was caught off guard when former servant revealed that his Bankai’s true strength was its power to generate a powerful poison, able to erode the cells of those infected by it. Using a fragment of Kamishini no Yari he'd left inside him, Gin caused Aizen's chest to dissolve so he could grab the exposed Hōgyoku. But instead of completely dissolving, Aizen instead evolved into a new winged form and teleported to the Hōgyoku's location to cut Gin down while reclaiming the item, saying the Hogyoku was his, even if it was not in his body. Rangiku soon arrived, rushing to Gin’s side and Aizen moved in on them, but Ichigo suddenly arrived. The former captain said he was disappointed upon sensing Ichigo's lack of spirit pressure, but Ichigo said that he wanted to fight away from his friends. Aizen refused, thinking that he couldn’t do a thing, but Ichigo grabbed him and dragged him out of Karakura Town to fight in a more open area, saying he would finish the fight in one moment. Aizen and Ichigo began fighting with Aizen saying they had both evolved to their maximum potential and that he understood that his own evolution was different from Ichigo’s which sacrificed his spiritual energy for superhuman strength. Though he expected to be the more powerful of the two, Aizen found Ichigo constantly besting him. Enraged, Aizen transformed again and went on the offensive before eventually managing to grab Ichigo and deeming him no longer worth keeping alive. However, slashing him across the chest to break free, Ichigo revealed his Final Getsuga Tensho to Aizen. Seeing the new form Ichigo assumed, coming to the conclusion that he has been surpassed, Aizen refused to accept it as he was hit by the Mugetsu attack. However, surviving as his body transforms, Aizen gloats over his now powerless opponent and was about to kill him. However, finding his body in pain as he returns to his original state, Kisuke arrived and reveals that a specially made Kido he made has finally been activated as the Hogyoku no longer deemed Aizen its master. Declaring his hated for Kisuke, Aizen demanded why one such as he would allow himself by Soul King. After Kisuke explains the Soul King's importance in preserving the Soul Society, Aizen retorted that victors can speak of the way the world should be before being completely sealing. Ten days later, a severely bound Aizen was brought before Central 46 for trial and is sentenced him 18,800 years in the lowest level of the underground prison. But Aizen's contempt for the verdict has his mouth and Hollowified eye covered with the sentence increased to 20,000 years.
Thousand Year Blood War arc
Seventeen months later, Aizen was visited by Yhwach who offered to release him. But Aizen turned down the offer, using his illusionary powers to deceive the Quincy's concept of time before realizing it too late.When the Soul King died, he was visited by Kyōraku who asked him several questions, but Aizen did not responded to him, Kyōraku thought that the seals placed on him restricted his ability to speak and unlocked several seals including the one in his mouth and told him that most of the people wouldn't be able to speak with their mouth sealed after two months, Aizen agrees to him and began to unlock other seals on his own while stating that hehas still two keys to use. After Shunsui unlocked his left eye and ankles, he began to talk to him, but an attendant attempted to bind him again, only to have his hands partially disintegrated by his Reiatsu. He was later brought to the surface and began to destroy the black creatures spawned from Yhwach and gave the instruction to the Shinigami's to crush them with Reiatsu. Aizen used Hadō #90. Kurohitsugi to kill a large number of creatures and then attempted to destroy the Soul King Palace with his Reiatsu, but his attack dissipated and Mayuri suddenly arrived to told him that his chair was created to block his Reiatsu and keep him in check. Aizen challenged him to pit his technology against his power, however he got interrupted by NaNaNa Najahkoop who attacked him from above. After recovering he conversed with Shunsui and watched the fragments of Lille Barro fall down from the Soul King Palace.
Much later, he saw Yhwach returning to Soul Society, he welcomed him to his Soul Society and the latter destroyed his chair while telling him why he is still interested to protect Soul Society, Aizen thanked him and stated that this has nothing to do with his interests and now he has the means to stop him from trying to rule over and control him. Aizen uses his powers to destroy the shadowy creatures that Yhwach produced from his body before creating a path to the Soul King's Palace. Aizen later battles Yhwach, playing a role in the final battle when he nearly gets himself killed using his Kyōka Suigetsu illusion to give Ichigo an opening to fatally wound Yhwach. In the end, hearing Yhwach's dying worlds following his defeat at Ichigo's hands, Aizen is returned to his cell. Ten years later, Aizen senses that the last remnants of Yhwach's Reiatsu have disappeared completely. He recalls Yhwach's final words about how his defeat meant the continuation of death and the fear accompanying it, remarking that the world Yhwach wanted would be a failed paradise. He states to create such a world would result in one which would be without hope. He remarks while people could go through life simply living, it does not compare to courageous individuals like Ichigo Kurosaki who are willing to face death and cut through fate without fear.
Aizen is completely calm and cold, having a very polite and knowledgeable manner about him and rarely showing an signs of alarm. He often tries to make small talk with his enemies so as to anger them. Aizen has an extremely cruel and dangerously manipulative nature, caring nothing for any of his subordinates and to him, they are all just pawns for him to use. He states that he doesn't have any morals, saying they just restrict his capabilities.
Aizen will stop at nothing to complete his plans and thinks of long and complex (as well as somewhat convoluted) plans. He often toys with his subordinates and controls his forces through respect, intimidation, fear, and mind games with only Gin being able to figure out Aizen's emotions. Aizen’s objective is to overthrow the Spirit King and states that he seeks to “stand in the heavens and end the unbearable vacancy on the world’s throne”. After mastering the Hogyoku, Aizen seems to have become less cautious in battle and has more of a severe superiority complex. He doesn’t think through his moves as much and believes that he is above Shinigami and Hollows. His intelligence and attitude make Aizen easily angered when heis fighting something he doesn't understand.
Powers and AbilitiesGenius Intellect: Arguably, the most fearsome trait of Aizen is his tremendous intellect. He is well-versed in the history, strategy, and tactics of Soul Society, and is privy to knowledge unknown to many, such as the existence of the Ōken and its method of creation. He has created several Hollows and Arrancar while avoiding any suspicion from the majority of Soul Society. For over 110 years, he had been engaging in experiments involving unique and highly dangerous manipulations of Reiryoku and Reishi, including experiments involving the Hollowfication of Shinigami, something which had never been done before. He has an innate knowledge of the Hōgyoku, rivaling that of its creator, Kisuke Urahara, even knowing how to destroy it. He figured out the true nature of Shinji Hirako'sShikai, allowing him to counter its effect. He effectively deduces the true nature of the Hōgyoku via trial and error of the situations which revolve around it.
- Master Manipulator: Aizen has proven himself very crafty and a cunning man since his public betrayal of Soul Society. He can deceive and manipulate others around him in different ways for a variety of purposes. For years, he convinced everyone around him he was a kind-hearted man with the best intentions for Soul Society while performing horrific actions. He has a great talent for analyzing and observing everything in his presence, allowing him to understand a person's pattern of thinking and better manipulate them. He can formulate well thought out plans several steps ahead of others, some of which have a long term in mind. His most well-known plan spans over 110 years, a great accomplishment which involved moving people around like pieces on a chessboard and making sure they played the role he had planned out for them. He is masterful at plans within plans, such as kidnapping Orihime, allowing him to use her abilities to extend the shelf life of the Hōgyoku and lure many of his enemies into Hueco Mundo to trap them, making it easier for him to accomplish the goal invading the Royal Palace. He can shatter the will of others. He has unnaturally high charisma, enabling him to gain the trust and loyalty of others and gaining significant influence over others.
- Master Strategist & Tactician: Aizen has proven himself to be a flawless and flexible tactician, adjusting seamlessly to any given situation, if not planning out events well in advance. He understands the strengths, weaknesses and mannerisms of his enemies, and creates strategies to achieve victory; this includes modifying an Arrancar for the sole purpose of defeating Captain-Commander Genryūsai Shigekuni Yamamoto, a Shinigami whose abilities surpass his own. Aizen is highly cautious , and leaves no blind spots. He is capable of consciously focusing, and being fully aware of multiple people, dangers, locations, tasks, e.t.c., and processing all of it at once without any trouble or confusion. He can notice, process and understand any/all details of any situation or environment no matter how small, allowing him to intuitively understand and solve any problem or situation no matter how difficult or impossible it may be.
- Shunpo Master: Aizen is so fast, opponents commonly cannot discern even being attacked by him until after it has taken place. Aizen can dodge simultaneous attacks at close-range and even when being attacked from behind.
- Immense Strength: Aizen is strong enough to stop the blade of Ichigo's Bankai with just one index finger and almost cut him in half with a single sword strike. He stopped Renji Abarai's Shikai with his bare hand and broke it with one swing, injuring Renji in the process. He stopped Komamura's Shikai with his bare hand, proving his strength is more than enough to combat someone of the same level.
- Immortality: Aizen attained immortality and nigh-indestructibility, he kept regenerating himself no matter the damage, resulting in the necessity to seal him away deep in the underground prison. He possesses apparently absolute immortality, he is unable to die, age, get sick, or seemingly be permanently wounded and is absolutely self-sustained. After being hit by Ichigo's Mugetsu, Aizen restores from the damage. He is later confirmed by Central 46 to having been left immortal by his interaction with the Hōgyoku.
Aizen possesses immense spiritual power, even for a captain-level Soul Reapers. He possesses incredible intellect, having knowledge on many things and high craftiness and cunning. Aizen is extremely skilled at manipulating others and always thinks a few steps ahead of his opponent and thinking out incredibly detailed plans with many steps. Aizen is able to adjust to any kind of situation in battle and has a great understanding of his foes, thus he can prepare to deal with them. Like all Soul Reapers, his primary weapon is his Zanpakutō, Kyōka Suigetsu, and he can activate and deactivate its Shikai ability with the release command, “Shatter”. Its ability is the power to completely hypnotize the opponent, controlling their senses so Aizen can create a variety of illusions to trick them.
To hypnotize the person, they have to see the release of Kyoka Suigetsu and from then on, the person will be completely under the hypnosis’ power. The influence of Kyoka Suigetsu can last for years as seen with the Visoreds, who were first hypnotized 110 years ago. The hypnosis can even affect the person if they are aware that they are being manipulated by it. However those with great power and ability can notice slight differences in the illusions, even if they can’t determine what they are. The only way to avoid being controlled by Kyoka Suigetsu is to touch the blade before its hypnosis power is activated. It is presumed that since Aizen is a captain, he can release the Bankai form of Kyoka Suigetsu, but he has never been seen using it. However, after his evolution prior to his capture, Kyoka Suigetsu corrodes away as his Zanpakuto's power has become a part of him. With the Hogyoku planted in his chest, it regenerates all of Aizen’s wounds and increases his strength and durability.
After his first transformation by the Hōgyoku, Aizen is in his “chrysalis” stage, possessing higher spiritual power, and increased strength, durability, and speed. After finishing his “chrysalis” stage, Aizen was even harder to harm, destroying the Kōtotsu by just having it collide with him, and even higher spiritual power, able to destroy souls just by being around them. In his third form, Aizen had greater strength and could teleport by breaking into shards, then reforming elsewhere. After transforming for the last time, he has a much more Hollow-like appearance and can fire powerful energy spheres from the skulls on his wings, as well as surround his opponent with an energy ring to destroy them.
- Aizen's Japanese voice actor Shō Hayami also voiced Zarbon, Frank Archer and Tokiomi Tohsaka.
- Aizen's English voice actor Kyle Herbert also voiced Metastacia, Masamune Nakatsukasa, Belphemon, Ho Yinsen, Karasu and Sir Lancelot.
- Aizen is very similar to Naraku. Both are responsible for the vast majority of atrocities in their respective series, both seek an incredibly powerful object (the Hōgyoku and Shikon Jewel, respectively) and successfully obtain them, making them the most powerful beings in their respective worlds up until their defeats. Coincidentally, both of these items started off inside the body of a heroine (the Hōgyoku was in Rukia Kuchiki's body, while the Shikon Jewel was in Kagome Higurashi's body). Additionally, both share many personality traits, the most obvious being that they're both extremely manipulative, and at some points, the similarities in their appearance could be found, both in their transformation states and to a lesser extent in their regular forms. Since Tite Kubo has admitted that he's a huge fan of Inuyasha, it can be safely assumed that the latter heavily influenced the former.
- He is the only Shinigami in the series to be considered Pure Evil.
- Aizen can be compared to Christianity's Lucifer in various decrees: The first is that both originally served a greater power before acting on their own whims to take control of reality. The second connection is that they manipulate others, gathering armies to aid in their endeavors. And lastly, being sealed away after the coup failed.
- Aizen's final form resembles the humanoid version of Lucifer's Red Dragon form from the Book of Revelation as painted by William Blake.
- The background music used in Aizen's final battle with Ichigo, Lucifer's Dance Parte B when he assumes his final form and Cometh the Hour Part A when sealed by Kisuke, are borrowed from the Hellverse movie.