Attended Enoshima Junior High and was known as one of the 4 Emperors of Enoshima P.S.4, denoting that he was one of the 4 strongest in the school. He is a strong fighter and is not afraid to go up against opponents that are stronger than him. His senpai at Enoshima Junior High was Kunito Nakajou, allowing him to gain in-depth inside knowledge of various gang-related information, particularly information about Midnight Angel. Tsukai attends Tsujidou High and quickly befriends the Onibaku upon their arrival and aids them in their quest for girls with Makoto, including hooking them up with Keiko and Mayumi, informing them about the Culture Festival at the Ferris School for Girls and the annual Valentine's Day parade. He also is willing to lend his friends a hand, such as offering to help Eikichi take revenge on Machida.