Sanada Yukio (真田 ユキオ, Sanada Yukio), along with his twin, are two of Shun's group's contrincants on the other side of the line while playing Shouben kouzou. They kill the rest of their team and appear to be very strong and fast. 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 the cross 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.
He later befriends the others from Cube 1 and also gets extensions in his hair, therefore resembling his brother. However, he says he didn't like his twin because he was always bossing him around and telling him what to do. He wasn't sad about his death.