Senzui is a fairly tall and slim man, his physique is similar to Saiga, being very well muscled. Senzui has medium long black hair that falls to his back and stands erect on the sides of his head. He dons what appears to be an ancient-like long sleeve shirt with a sash tied across his waist, under his shirt is a chain-mail vest which supports his ninja appearance (similar to Shigure and Kenichi). Senzui also wears gauntlet bands around his arms and legs with soft ninja shoes.
Senzui is a very cunning and manipulative man. He was the mastermind behind the Eternal Sunset operation all along, meanwhile impersonating Saiga Furinji, willing to make everyone believe that all his actions were Saiga's, even putting Miu (Saiga's daughter) against him, forcing her to believe that Saiga was Shizuha's (Saiga's wife) killer.
His most important quality is his indifference and merciless attitude towards innocent people, having claimed he does not have any remorse or mercy in killing anyone in order to fulfill Eternal Sunset plan, claiming that the plan is top priority over everything else (even the human life). This even extends to his own disciple Kajima, as after the latter used a forbidden move solely to advance martial arts and cost him his left eye, Senzui expressed little remorse and refused to let Saiga help him.
However, Senzui wasn't always a ruthless man. As during the war with the Kuremisago and the Liberationists Senzui still maintained some of the Katsujinken beliefs along side his former friend Saiga. However, with the number of lives being lost on the battlefield left him to believe that the war would never end. To that end, he was influenced by the elders of his clan and ruthlessly murdered his own people to cause discourage on both sides while disguised as Saiga to ensure he wouldn't lose face to the public and label Saiga as the culprit to reafirm the clans beliefs. To that end, his lack of morality on life is further extended during the Eternal Sunset as he was more than willing to bomb numerous countries while exhibiting a hypocritical nature stating it was all for "peace". Also, according to Saiga Senzui didn’t want the Eternal Sunset to happen and it was due to Mikumo Kushinada influence that he started to plan for it.
Due to his Kuremisago heritage, he believes that emotions on the battlefield or in martial arts are useless. This extends in battle as well, as when he murdered his father (albeit indirectly) he expressed little remorse. However, he was shocked by the deed somewhat.
He even stated that all of his actions like the killing of Saiga's wife and attempt of his daughter was merely a compensation for Saiga's mistakes. Despite his beliefs about emotion in martial arts being useless, he still showed some level of remorse (albeit very little in amount). Even after killing Shizuha, the woman that he loved, he could't killed Miu as a baby and left her alone in the snow, shedding a single tear by the atrocious act that he just committed.
Senzui was born the leader of the Kuremisago clan. He was designated by the clan to marry Shizuha. One day however he met Saiga Furinji and, despite their initial quarrel, they became friends and even rivals who trained on a daily basis. He also approved of Saiga marrying Shizua while most opposed of it due to him being an outsider.
After Saiga and Shizuha Furinji tried to ask for her hand in marriage the most conservative people (Senzui supported the union) opposed to it while some others turned over Saiga and Shizuha's side in order for a new way of life. That forced into a feud driving the clan into two sides that eventually fought bloody battles around the world, one which resulted in Senzui (albeit indirectly) killing his own father. After many battles caused many Kuremisago members to pass away and Senzui to do something to Saiga and asks for Saiga's forgiveness for what he is about to do.
With that, Senzui, while disguised as Saiga began killing off many Kuremisago members in an effort to stop the fighting on both sides. He is commended by an elder for his cold-bloodedness in killing his comrades and is reminded to stick to his promise so that the traditionalists will reach a compromise with the liberal faction and end the fighting. Another elder states that Senzui will be made one of the elders of the Kuremisago after the fighting but he says that he does not matter to him, as he only wishes the fighting to end with the least amount of casualties. He is then ordered to carry out his goal to the end, and for that he needs to kill Shizuha and her child.
At some point after that, Senzui killed Shizuha while pretending to be Saiga plus marking baby Miu memories making her believe that Saiga was the one who killed her mother. He choose to leave Miu alone out of respect towards Saiga and his love of Shizuha. Then some time later joined Yami and became the One Shadow of the One Shadow Of The Nine Fists as well as one of the rulers of the organization itself. He then became the master of Kajima Satomi along side Saiga who, at the time, was unaware that Senzui murdered his wife.
Senzui is a very skilled master of the Kuremisago Style and the strongest member and head that the Kuremisago clan has ever produced. His combat prowess was able to easily defeat famous masters like James Shiba and Akira Hongo (although both fighters were in a handicap state of their own nature). Senzui is a master of disguise as he was able to fool even a sharp mind like Akisame Koetsuji into believing he was Saiga. His skills were able to overcome Shizuha's own power and skills. He is the best Lineage within the Kuremiasago.
- Master Ninja: As Senzui is stated to be the strongest member and head of the entire Kuremisago Clan, he is no doubt a powerful ninja and by extension assassin. This is evidenced in the fact Senzui was able to stealthily assassinate nine skilled members of the liberal faction when he was manipulated by the clan elders. Despite doing the assassination of the liberal members in the open and left their bodies to be discovered, nobody was able to suspect Senzui of being the perpetrator.
- Immense Strength: Senzui possesses enormous strength, capable of defeating a powerful S-rank boxer such as James Shiba (after having already fought Akira Hongo) with two fingers and seriously wound him with little effort. Just clashing with Saiga together resulting in a large steel cage door being smashed to pieces with nothing but raw strength. It was shown in the past that during Saiga's visit to the Kuremisago's village, Senzui was able to easily balance one end of an enormous boulder with just his index finger while Saiga balanced the other end. Later on in the flashbacks, Senzui's strength is enough to easily pierce and kill fellow clan members and ninjas of the Kuremisago Clan including very skilled ones despite the training they underwent made them powerful fighters.
- Disguise Master: Like Saiga, Senzui has great skills in disguises, such as how he disguised himself as Saiga Furinji and no one, not even anyone in Yami or the Hachio Executioner Blade knew of his true identity. The fact he was able to supress his ki around numerous high class masters, even a grand master of Mikumo Kushinada's level a testament to his amazing skills in supressing his ki. Even while fighting powerful masters such as Hongo and Shiba individually neither were able to tell the real from fake. In fact a testament to his disguise skills is the that he was able to trick even Shizuha Furinji into believing that he was Saiga despite the three of them being very intimate with one another with the latter two being husband and wife.
- Immense Speed: Senzui's speed is amazing, as he's capable of making numerous clones of himself against Hongo and even outclass him in every corner of their fight. Even a grand master of Saiga's level must keep his guard up just to be able to keep up with Senzui's speed.
- Immense Agility: Senzui is extremely agile where he was able to easily fight against Saiga in mid-air and had propelled himself on multiple surfaces of their surroundings to keep himself airborne with complete control over his movements.
- Immense Endurance: Senzui also has powerful durability as he continued fighting against Saiga despite receiving grievous injuries from the latter's techniques that were powerful enough to destroy their surroundings to hold on to the missile detonator.
- High Intellect: Senzui is a remarkably intelligent and cunning man, having been able to fool all of Yami into believing he is Saiga Furinji and even the elder, who is regarded as the Invincible Superman to believe that his son murdered Shizuha. Even Saiga commended his intelligence being far superior to his own.