Kamisama no IutooriEdit
Shouben Kouzou and later gamesEdit
Yukio and his twin brother appear as the last remaining two-man team, having killed the rest of their team, on the opposing side of Shun and the others during the Shouben kouzou game. Using tactics involving throwing food balls to slow down the other team, they defeat three teams on Shun's side. Then, along with Shun's group, they win the game and pass on to Urashima Tarou's castle. However, Yukio's twin dies when he picks up an "X" sign from a bowl Tarou gave them. Yukio is one of the survivors that manage to get out of the cube on top of the hospital.
Three months later, Yukio returns to participate in the Children of God Sports Festival along with the other survivors from Cube 1. He passes the first game, Courage race, by lifting the nutcracker doll that was chasing him and throwing it on another contestant who tried to knock him down earlier. In the next game, Boutashi (Pole Toppling), he serves as the first line of defense for his team.
Kamisama no Iutoori NiEdit
After Shun and Amaya fail to kill Kamimaro and the playing field becomes chaotic, Yukio manages to escape to the Amanojaku Labyrinth and is found by Akashi in the rope room along with Aoyama. He steals a key from Aoyama, but also saves Akashi from falling to his death, then goes off on his own.
Three Kingdoms Cops and RobbersEdit
In the next game, Three Kingdoms Cops and Robbers, Yukio is found aligned with the Star country. When the Sun country attacks, Yukio gives a speech to rouse the Star country defenders while being attacked by Dandelion, then defeats his enemy but also suffers a grievous wound. He survives however, and joins the others in the final battle against Lily the Sun king. Moments before the game is over, the Star king is sent to the Sun prison and executed, causing the Star country to lose and all its members killed, including Yukio.
Yukio is an overly easygoing guy who does what he wants and pays little attention to others. He maintains a poker face most of the time and rarely shows emotions. When he first appears, he has a shaved head in contrast to his twin brother's long hair. After surviving the cube games he gets extensions in his hair, making him resemble his late brother. He says he didn't like his brother because he was always bossing him around and telling him what to do, although the two can display a high level of teamwork as seen in the Shouben kouzou game. Despite his indifferent attitude, Yukio can show compassion to those who he recognizes as "a good person", such as when he rescues Akashi. He is also capable of leadership when presented with the task as he managed to rouse the Star country to hold against the Sun country's fierce attack.
Yukio possesses amazing physical abilities, able to run very fast and fight against a large number of people without giving out. His endurance is also extraordinary; he can quickly recover from being hit and survive wounds that would kill a normal person.