Tsutomu is Arimi's classmate who has been in love with her since elementary school. He is Ginta's cousin. Tsutomu is loud, obnoxious and a crybaby. He is constantly thinking about the past and is jealous of anyone Arimi dates. He also has a habit of making challenges to Ginta or Yuu or both of them together. He always loses, and has to shave his head. He really blows a gasket when it looks like Ginta is dating Arimi. He follows them everywhere making everyone's life miserable.

In the New Year's episode, he meets the girl of his dreams, Yayoi-chan but he forgets to get her name, address or the name of her school. He is devastated. He is sitting in a park, feeling rejected in the Valentine's episode when he overhears a guy turn Yayoi down. She sees him, recognizes him and they share the chocolate that she was going to give the other guy. We see them again in episode 58 on a double date with Ginta and Arimi. It looks like he is going to be a good guy after all!

When Ginta and Arimi break up in a later episode, he teams up with Miki to get them back together. By this time, it really looks like he is maturing.