A talented but troubled pianist, Kai is Miki's coworker at Bobson's ice cream parlor. He falls in love with Miki and attempts to drive a wedge between her and Yuu by using Miki's lost medallion, which had a picture of Yuu, to fabricate a lie about her true feelings for him. His plan nearly succeeds, but ultimately fails when Yuu takes a trip outside Tokyo and realizes how much he misses Miki, prompting Miki to confront her own flaws. When they reunite, Miki and Yuu reconcile.
Later, a more mature Kai reappears, offering Miki his sincere and unconditional support after Yuu leaves to study abroad. He doesn't expect Miki to forget Yuu entirely; instead, he aims to help her through her emotional struggles. Miki appreciates his companionship and even dates him briefly, but she cannot fully move on from Yuu. By the end, it is hinted that Kai may eventually get together with Suzu Sakuma.
