Kei Tsuchiya  

, 土屋 蛍

Mikis coworker at Bobsons ice cream parlor was a talented pianist who struggled with personal issues. He fell in love with Miki and used her lost medallion, which had a picture of Yuu, to fabricate a lie about her feelings for him. Although this almost succeeded, it failed when Yuu made a trip outside Tokyo but couldn't enjoy it because he missed Miki too much. This caused Miki to confront the worst parts of herself. When they saw each other again, they reconciled. Later, a more mature Kai reappeared and offered Miki his unconditional support after Yuu went abroad to study. Although Kai did not require Miki to forget Yuu completely, he was happy to help her through her struggles. Miki appreciated his company and even dated him briefly, but she couldn't compete with Yuu. It is implied that Kai may or may not end up with Suzu Sakuma at the end.