Overall, Riddhe is a loyal, well-spoken, and fearless soldier. Despite this, his lavish and isolated upbringings have sheltered Riddhe's views on the world. Though he is the heir to the influential Marcenas family, he enlisted in Londo Bell to escape his family that he is uncomfortable talking about. He believes that the Earth Federation, even when there was corruption, would eventually do the right thing. However, his views eventually change and he is willing to disobey the rules in favor of doing what is right. After being told the truth about Laplace's Box and his own family, Riddhe became determined to protect the current world order and the billions of lives that reside within it, even though it's flawed.
Riddhe is also a believer in luck. For that reason, whenever he goes into combat, he wears a bracelet with a miniature biplane attached, which he calls his good luck charm.
During a battle at Anaheim Electronics' Industrial 7 space colony, the colony was attacked by both Londo Bell and the Neo Zeon remnants known as "The Sleeves" with both parties aiming to claim a mysterious item known as "Laplace's Box", more specifically the key to the box which resides in a mobile suit. Eventually, Riddhe launched from the Nahel Argama in his RGZ-95 ReZEL and found a trio of teenage civilians (including an incognito Mineva Lao Zabi) and rescued them, escorting them to the Nahel Argama aboard a shuttle. Later, he picked up a mysterious single horn unit after it transformed into a Gundam and engaged "The Sleeves'" large mobile suit.
Once the Nahel Argama was far away from Industrial 7, Riddhe was among the ReZEL on patrol. His squadron leader, Commander Norm Basilicock, reminded him that it is not luck that keeps him alive. Romeo Squadron then spotted an incoming vessel. At first, they believed it to be an enemy, only to discover that it was a derelict ship, Salamis-class, moving on its own backup power system.
Romeo Squadron was recalled to the Nahel Argama, upon which Riddhe disembarked. He then spotted one of the civilians he rescued, Audrey Burne, who was asking Ensign Mihiro Oiwakken about who was piloting the Gundam. Riddhe offered to show her a good spot to observe the Gundam. Though Mihiro tried dissuading Riddhe, he assured her that it would be fine. Just then, another civilian Takuya Irei popped up, exclaiming his knowledge of how the Nahel Argama was the mothership of the Gundam team during the First Neo Zeon War and was now carrying the new one. Mihiro offered to come along too, stating that if that Gundam didn't show up when it did, she and Riddhe would not be having this discussion; she in particular, wanted to meet the pilot who saved their lives.
While observing the Unicorn Gundam, Riddhe recognized something familiar about Audrey, which made her apprehensive. He noted that she looked like Natsume Swanson, a famous actress, to which Audrey stated that she doesn't know much about the entertainment industry. Takuya then drew Riddhe's attention, as the Nahel Argama technicians finally opened the hatch, revealing his friend, Banagher Links, inside.
Battling "The Second Coming of Char"
While trapped within space debris, Neo Zeon forces found the Nahel Argama's position after Captain Otto Midas brashly fired at the derelict ship, exposing their location. As Riddhe moved to the hanger, he passed by the infirmary where Banagher was recovering. Riddhe lost his good luck charm, which Banagher caught while it was floating about and called Riddhe. He thanked the young lad and reassured him that he and the MS corp can protect the ship. As he moved away from Banagher, Riddhe could only think to himself that the young boy could pilot a Gundam.
Once Riddhe got in his ReZEL, he was teased over the comm by Lieutenant Homare, asking "Is the rich kid getting cold feet?" Riddhe smoothly denies it, before launching. No sooner had he launched, was Homare shot down by a single red mobile suit. Angered at the loss of his comrade, Riddhe impulsively tried shooting down the red MS. When he missed and vaporized an asteroid, Norm ordered him to stay in formation. As the red MS took out a Stark Jegan and Riddhe's ReZEL's right leg, Commander Daguza Mackle announced over the comms that they are holding Audrey, revealed to be Mineva Lao Zabi, the Princess of Neo Zeon, hostage, in an attempt to negotiate safe passage. Once negotiations broke down, Riddhe charged against the red MS, angry that Mackle would perform such a maneuver against terrorists. The red MS was about to take a shot at him, forcing Riddhe to back off. Norm engaged the red MS with beam saber combat, telling Riddhe to control himself. But the red MS overwhelmed Norm and killed him. Enraged at this, Riddhe drew his beam saber, only to sense the Unicorn Gundam, piloted by Banagher, joining the fight to give the Nahel Argama time to escape. Riddhe teamed up with Banagher and tried valiantly to take down the red mobile suit. However, an intervention from the NZ-666 Kshatriya disabled Riddhe's ReZEL and Neo Zeon managed to capture both Banagher and the Unicorn Gundam.
Speaking to the Princess
Back on board the Nahel Argama, Riddhe visited a captive Mineva, who had taken the pseudonym of Audrey Burne. Riddhe explains to Mineva that as a child, he remembered seeing Gihren Zabi make his famous "Sieg Zeon" speech at his brother Garma's funeral and how he was fearful of the Zeons. And he could guess that Zeons still say that chant and demanded that she say it. Getting only silence as a response, Riddhe then asked why the Princess of Zeon would risk her own life to stand up to her people. Getting more silence, Riddhe coldly stated that perhaps the professionals can get an answer out of her. Before he leaves, Riddhe told Mineva that Banagher called her name as Audrey, not her true name.
Mineva then questioned if the Federation will actually interrogate her. She explained that the public would not be informed about her being on board the ship. Mineva then asked why Full Frontal would vehemently refuse to believe that she was the real Mineva Zabi. Riddhe replied that he was trying to stall their negotiations, but Mineva then told him to think about how she was able to avoid capture before the Gryps Conflict and how Neo Zeon was able to maintain military training grounds within the Earth Sphere. Riddhe asked if there were backroom dealings, and Mineva explained that while it wouldn't be easy for the families of the Industrial 7 incident to get over the matter, Spacenoids like herself were used to injustices. She also said that the Federation had been using Neo Zeon as a scapegoat for the people's frustration, painting them as being just as tyrannical as the Zabi family. Mineva also told Riddhe that the Federation was trying to end the conflict with Zeon and that was the reason why the Vist Foundation had to give up Laplace's Box (the original Universal Century charter). Riddhe then explained that he was always trained as a normal MS pilot to fight in combat, and had the conviction through his sheltered life that the Federation would eventually resolve its issues. Mineva shared the same sentiment, having to live through the Zabi family's political bickering and how the Zabis shouldered the blame for the One Year War. Mineva told Riddhe that she was willing to sacrifice herself to make sure that the same mistakes her family made would not be repeated. A Federation soldier interrupted them, informing Riddhe that there was movement around the ship. Riddhe explained to the soldier that they were being resupplied by a Columbus-class ship. He turned back to Mineva, reminding her that regardless of backroom dealings, she and Neo Zeon were still the enemy and responsible for the death of his comrades, something he will never forgive. Mineva simply responded of course he won't.
As Riddhe turned to leave, Mineva asked him if his surname is really what she thinks it is, having a shrewd idea what family he is from. Looking away, Riddhe confessed his wish that they didn't have to meet like this. As soon as he left, Riddhe mumbled to himself that there was a lot he would like to change.
Road to Earth
With his ReZEL damaged beyond repair, Riddhe received an all-new unit, the transformable MSN-001A1 Delta Plus. During this time, the crew of the Nahel Argama and ECOAS tried to figure out a way of getting back both Banagher and the Unicorn Gundam from the Neo Zeon asteroid Palau. While the politicians and bureaucrats argued over what resources and manpower should be needed for the operation, Riddhe chose to spring Mineva from the Argama to take her to Earth.
As they snuck through the ship's corridors, Riddhe explained the details of the upcoming operation: the Federation will separate Palau's four asteroids, then use the Nahel Argama's hyper-mega particle cannon to seal off the military port, at which the Federation will then concentrate attacks on the Sleeve forces, using the chaos to extract Banagher and the Unicorn Gundam. As soon as they arrived in the hanger, Riddhe informed Mineva that he could only scrounge up a few rations for the journey to Earth using the Delta Plus, due to its ability to make an unassisted atmospheric re-entry. Mineva wasn't concerned. Then suddenly, they were discovered by Micott. Assuming that Riddhe was betraying her and the Federation, Micott went to grab a phone to alert the ship. Luckily, Mineva was able to dissuade her. Micott reluctantly relented but reminded Mineva that she doesn't forgive her.
Riddhe was able to get Mineva aboard his MS and they launch into battle. As the Sleeve forces begin retaliating, all MS sortied from the Nahel Argama were ordered to assist ECOAS. Riddhe was reluctant to fight, knowing that he may kill many of Mineva's subjects. Mineva encouraged him to follow his heart, otherwise he may regret it. Riddhe then proceeded to disable three Sleeves MS, before they both noticed the Unicorn Gundam soaring through space and realized that Banagher must be piloting it. They get in contact with him and explain their plans to go to Earth, where Riddhe's father, Ronan Marcenas, an advocate of spacenoids, can help them resolve the conflict before it escalates. Banagher accepted the plan and holds Riddhe's promise to protect Audrey. Riddhe then noticed a mass driver in Palau's port and attached it to his MS to boost their journey towards Earth. As they leave Sleeve airspace, Riddhe received Federation comm chat indicating that the Unicorn had returned to the Nahel Argama, having captured the NZ-666 Kshatriya. He also indicated to Mineva that he would probably be counted as KIA. The two then bypass the Earth's absolute defense line with assembly privilege and make a successful atmospheric re-entry and make it to his family mansion.
Curse Bound by Blood
As soon as they arrived, Riddhe's father, Ronan was put in a difficult situation. After he gets off the phone with Martha Vist Carbine, he commented that his son must have fallen for Mineva. Ronan told his son that he never dreamed he would get involved with Laplace's Box, and that the only way out was knowing the truth behind the Marcenas family. As Riddhe later explained to Mineva, his family must have blood on its hands as the Vist Foundation to maintain their political power throughout the Universal Century. He realized that in order to protect Mineva and end the conflict, they have to locate the box before either the Vist Foundation or Neo Zeon does, which means finding the Unicorn. Failing that, their only other option would be to try and destroy it. Riddhe hugged Mineva and promised to protect her despite the current situation. Riddhe then proposes to her, hoping that a marriage would get his father to listen, but she declines. In frustration, Riddhe rode away from the mansion on a horse and lied in the grass onto the night.
Riddhe was soon transferred to the Ra Cailum to serve under Captain Bright Noa, a veteran of many wars and the frequent leader of Gundam teams. In meeting with the Captain, Riddhe was told by Bright that they were heading for New Guinea where they lost contact with the Bonefish. Bright stated that its sinking might have been connected to the Garencieres and the box. Riddhe asked Bright not to give him special treatment on missions, but Bright replied that Riddhe is just a soldier to him, asking him to return alive however. While Riddhe looked at a picture of Amuro Ray, Bright was informed that the Garencieres has lifted off.
Riddhe was to launch with the Tri-Stars to assist the Battle of Torrington, though the latter jokingly warned that if he got in the way, they'd shoot him down. In the midst of the fighting, Riddhe heard Banagher's voice, learning that he was trying to talk down Loni Garvey/AMA-X7 Shamblo. Riddhe/Delta Plus flew to his position and rescued him from the clutches of the Shamblo. Riddhe told Banagher that no amount of reasoning can change Loni's mind and that the only solution is to destroy the Shamblo to stop its rampage. Banagher disagreed, believing that using force won't solve the problem. The Gundam broke off from Delta Plus and landed, with Riddhe stating that Loni was trapped by the same cursed bloodline he and Mineva are a part of.
As Banagher's attempts to talk Loni down fail and herself going berserk at the death of her surrogate father, Banagher activated the NT-D but failed again. Banagher/Unicorn hopped on the Delta Plus as Riddhe said they have no choice but to kill Loni now. In order to do that, Riddhe said they have to be faster than the reflector bits. Riddhe circled them around and lined Banagher up for a shot but he hesitated. Riddhe tried to convince Banagher to shoot, stating that it was pointless to risk his life for a mere possibility. Ultimately, Banagher couldn't bring himself to kill Loni, so Riddhe grabbed his beam magnum and fired, incinerating Loni and stopping the Shamblo, though the recoil of the powerful Beam Magnum greatly damaged the Delta Plus' arm.
Riddhe then received orders from Bright to capture the Unicorn Gundam. Riddhe was more happy to do so, since he believed that the whole war was Banagher's fault as he pointed a beam rifle at the Unicorn and told Banagher about his orders to capture it. But before either pilot could react, they spotted the RX-0 Unicorn Gundam "Banshee" descending from the sky and transforming into a Gundam.
As the Banshee engaged its weapon, Riddhe fired at it, in which it dodged and fired its weapon in retaliation. Riddhe took cover beneath the inactive Shamblo, only for the Banshee to slice the massive mobile armor in half, pinning Riddhe/Delta Plus. The Banshee took advantage of the confusion to capture Banagher/Unicorn.
Aboard the Ra Calium, Riddhe argued with Alberto Vist and questioned him about the second Unicorn Gundam. As he was about to stop Alberto Vist from walking away, Marida Cruz stopped Riddhe from touching him. Alberto then revealed that Banagher is his half-brother.
After some time, Riddhe was assigned to help guard the Unicorn Gundam to the Vist Foundation's Garuda-Class Ship. Suddenly, the carrier was ambushed by the Garencieres. In the confusion, Banagher escaped and fought the Banshee. Listening in on radio chatter, Riddhe realized that Londo Bell is collaborating with the Garencieres and ascended to the Garuda-class to try and rescue Mineva Lao Zabi. As she asked why he was doing this, he responds that he was trying to stop the Zeons from ruling the world. Alberto cut in that the Vists were working to claim the Box and stated that Mineva understood this. Riddhe angrily lashed out at Alberto, reminding him that his grandfather, Syam Vist, was equally responsible. Riddhe said that Syam had luck on his side when he found the Box and used it to gain power in the Federation, but Zeon called for Spacenoid independence, followed by the One Year War, which made both Syam and the Federation government realize the power of the Box. Mineva realized that Riddhe knows what the Box is and said that it's everyone's right to know. She felt Banagher's presence, but Riddhe wanted her to join him and said the Unicorn is dangerous. The "curse" of the Universal Century was the revelation that Newtypes existed, and Mineva wonders what he means. Riddhe said that even if he lived in an imperfect system, he'd fight to defend it.
But before he could say more, they came under attack from Suberoa Zinnerman, who used cover fire and smoke to cover Mineva's escape. Riddhe went after Mineva as she clung to the edge of the hangar, damaged by an exploding Anksha that came too close to the Unicorn and Banshee's psychofield. As he made his way to her, Mineva told him that she is a Zabi, and that she'll find out the Box's meaning for herself, which she preferred to war. If the imperfect system that Riddhe spoke of only stifles mankind, then she'd be committing crimes as great as her father and grandfather. Riddhe asked if she wants to fight the world alone and said that no one believes that the world will change and that no one cares about a future they won't live to see, but Mineva stated she was not alone in her fight. In the end, Mineva did not accept his help and decided to free-fall, calling out for Banagher's help instead. Banagher rescued Mineva and placed her in the Garencieres. Riddhe returned to his Delta Plus, crying over having lost Mineva.
Banagher went back to his fight with Marida, during which he traps her in the Garuda-class. Riddhe, upset about being unable to help Mineva, aimed at both Gundams with his Delta Plus and prepared to fire. He was spotted by Marida, in which she confused him for a Gundam and tore the Delta Plus apart. Riddhe fell out of the Delta Plus while Marida was confused as Banagher tried to calm her down, starting to fire gunshots at the Banshee, calling it "Gundam", making Marida realize that her enemy was "Gundam" in general and yet she was piloting a Gundam herself. As Riddhe ran out of bullets, he started gasping for air due to the high altitudes, having forgotten to put back on his helmet and was forced to find an oxygen mask. He then looked up towards the unmanned Banshee, dropping his good luck charm.
Banshee's New Pilot
Returning to Earth, with the aid of Alberto, Riddhe became the Banshee's new pilot. He also asked Riddhe to both destroy the Unicorn and take back Marida, and said that if he failed, then the Vist Foundation would use its "last resort". Riddhe asked if Alberto was fine with killing Banagher, his own half-brother, and Alberto responded that their path is already stained in bloodshed. He implied that he purposely shot his own father and further states that the Vist family had a long history of killing family members, with Martha's father being killed by Syam Vist, and he believed that Martha was declaring a war on men.
Riddhe then boarded the RX-0(N) Unicorn Gundam 02 Banshee Norn and took a shuttle into space. He then tested out the Banshee in a debris field before boarding the General Revil.
Catching up to the Nahel Argama, Riddhe engaged his former comrades. He fired at a Jegan riding a ReZEL, destroying its shield. His opponents then lured him into a trap, unleashing inflatable dummies but Riddhe bested them all, disabling their MS. He then started searching for the Unicorn and spotted it above him. Riddhe/Banshee and Banagher/RX-0 Full Armor Unicorn Gundam then clashed beam sabers.