Was part of Punpun's badminton club in middle school and Aiko's ex-boyfriend. He got a wound to his leg, though he refuses to assume it and continues playing badminton. He looks truly in love with Aiko and he says she's her first girlfriend and she's apparently the one who asked him out. He doesn't know how to act when he's with her and he's very shy. He talks about her with Punpun, and the both of them become friends. When he finds out Punpun and Aiko has a relationship, Yaguchi tells he's the one who's gonna protect Aiko, and if he loses in the badminton tournament, he'll give up on Aiko. Badly, his wound makes him fall and he loses his match.