Jin is the resident of room 103. Jin is a third-year student of Suiko. He is Misaki’s childhood friend and a playboy. He has dated several girls, including Misaki’s elder sister, but in the end he breaks up with all of them.
Jin has feelings for Misaki, but he feels he is not good enough to match her, so he ended up becoming a playboy. He finally becomes a couple with Misaki during the fifth novel. He wants to become a playwright, and later attends a university in Osaka to achieve his goal. To pacify Misaki, he gives her a marriage registration form with his signature as a warranty, but Misaki ends up turning it in after his departure on the same day, which makes them officially married.