He is one of the handsome boys in Hoto High School, just like Akihiro. He is very good at sports and has always been Akihiro's rival. The two have been friends for a long time and are very close, but he is not good at studying. He is someone who often forgets to wear a tie to school, but he is not as innocent as Akihiro. He often indirectly tells Akihiro why he is hated by many boys in school, but Akihiro never knows about it. He has a girlfriend, but he does not reveal it to anyone except those he trusts so as not to cause problems with his girlfriend. Kai usually attends the sports club most of the time.