Kappei Inagaki attends Misaki High School, standing tall with black hair and brown eyes. He typically wears his school uniform or casual outfits featuring a black t-shirt, blue-and-yellow coat, and blue hat.

Naturally friendly yet awkward, he occasionally stumbles through actions. Kappei shares close bonds with classmates Ayane Mitsui and Kayoko Nakajima. He persistently invites Ayane to kickboxing matches, though she always refuses.

His dedication to the kickboxing community surfaces when he brings magazines showcasing Ayane's achievements to school. This unintentionally reveals her secret participation in the sport to faculty, risking her expulsion due to policies banning violent extracurriculars.

At Ayane's debut fight, Kappei cheers loudly, comments on the bout, and snacks on popcorn. He shows visible shock upon learning of her involvement, especially when she battles professional kickboxer Sakurako Miyagawa, having believed Ayane disliked the sport.

Rushing to class one day, Kappei drops a kickboxing ticket later found by the principal, further exposing Ayane's activities.

Despite her rejections, he consistently admires her kickboxing career and vocally supports her matches. He demonstrates kindness by praising Ayane's skills to others when discussing her accomplishments.

Kappei maintains a good-natured friendship with Kayoko Nakajima. Both champion Ayane's pursuits, though Kayoko exhibits deeper concern for her well-being and the fallout from her secret kickboxing.