Ryo (known as Kai in the anime) was a human and a student underneath the martial arts master Mitamura, as well as a former member of Team Ichigaki during the Dark Tournament Saga, where he was brainwashed by Dr. Ichigaki and referred to as M-3. Kai is now an ally of Yusuke Urameshi. He was called Hans in the Filipino dub of the anime. He was voiced by Daiki Nakamura in the Japanese version and in the English dub by Mike McFarland. In the Filipino Dub of the anime, he was voiced by Eric Resurreccion which also provides Kai's voice.
Ryo appeared as a young man with slick brown hair, blue eyes, and a small Frankenstein-esque cross-shaped scar above his right temple, as well as being typically shirtless exposing his well-toned body, wearing only a pair of black pants with red highlights and black boots. His eyes were blood-red in color when under Ichigaki's control, but reverted back to their natural blue after he was freed from his brainwashing by Genkai as Masked Fighter.
In the flashbacks where their master Mitamura was sick (revealed to have been poisoned by Dr. Ichigaki), Ryo wears a blue and white jersey jacket to conceal his well-toned body from his current outfit.
Ryo, along with En and Kai, were students under martial artist master Mitamura. At one point in time, Mitamura contracted some sort of disease. Not having the 7 million necessary to treat him, the students were helpless until they were approached by Dr. Ichigaki. Ichigaki promised to cure him for free in exchange for them being guinea pigs in his scientific experiments. However, unbeknownst to them, Dr. Ichigaki's true purpose was to brainwash them and use them as mindless slaves to fight for him.
Dark Tournament Saga
He made his debut alongside the rest of his team in the Dark Tournament, facing and killing a member of an unnamed team in the early rounds of the tournament. He, alongside En and Kai, fought Yusuke, Kuwabara and Genkai in a 3-on-3 battle royal. In the anime, the 3 brainwashed students' teamwork was flawless, putting pressure on Team Urameshi and soundly landing blows on them. The trio would come to cause severe damage to Kuwabara, who refused to kill them, knowing they were innocent humans (before the actual fight, Kuwabara had a dream about their whole ordeal). Ultimately, his & his teammates' lives were spared when they were returned to normal by Genkai's energy attack, finally freeing them from Dr. Ichigaki's control. He & his teammates had a tearful reunion with their master, who had been healed by Kurama.
Ryo wants to fight on Yusuke’s team in Kuwabara’s place, but Yusuke says Kuwabara would kill him if he let Kai do that, and it’s against the tournament's rules anyway. In the manga, Ryo just says “oh, right” and that ends the conversation. Later we see him and the rest of his group react to stuff as Round 3 begins. In the anime after Ryo’s “oh, right”, Yusuke tells him to go take care of his master. Kai thanks Yusuke, became an ally of him, and runs off to join the others, and we see them leave the stadium, giving them more closure.
He also appears alongside En, Kai, and Mitamura during the final battle between Teams Urameshi and Toguro as part of the audience since En, Kai, and Ryo were now allies of Yusuke. In the anime, Kai's soul starts to be awoken by Younger Toguro's soul absorption technique for consumption, much to the horrible shock of both Ryo and En.
- In the manga, during Round 2 of the tournament, it was established that these three guys are named “Kai”, “Ryo”, and “En”, but it wasn’t clearly established who was who aside from Kai (the one who used the staff). Most likely, the anime decided back then that Ryo was the one with the staff, and decided to stick with that in spite of the manga. The Spirit World Who’s Who guidebook identifies “Kai” as the one with the staff (in keeping with the manga version), “En” as the one with the throwing discs, and “Ryo” as the one with the claw attack.