As a child, he enrolled in a karate dojo, but years later, his parents made him quit to focus on preparing for junior high school. He and Madoka Tokumaru, who previously worked part-time at the dojo, work together to resolve their differences. During this period, Shunpei admits that he admires Tokumaru despite his earlier conflicting behavior and strives to surpass him.
In "Yume Musubi, Koi Musubi", Shunpei speaks of an unrequited love, which is revealed to be Tokumaru in "Koi Cha No Osahou". Sadly, he was rejected after confessing his feelings, yet he continues to attend the dojo and remain by Tokumaru's side.
