He is Akihiko's room and classmate, and on-again-off-again boyfriend as well as a University student.
He has been classmates with Akihiko since their high school days. Though he is Akihiko's roommate, he sometimes goes abroad and sometimes he stays in Japan.
During the summer of his first year of High school, Ugetsu meet Akihiko while he is playing his violin in the music room. At first, he asks him who he is, but he soon recognizes Akihiko as the boy who placed second at the violin National level competition that taken place the previous day. Ugetsu says that he thought Akihiko’s rendition of Brahms was good.
Later Akihiko becomes his first friend and then his boyfriend. In the spring of their third year in High School Akihiko, using his parents’ divorce as an excuse, comes over to live with him. After they graduated, around the time Ugetsu started actively performing as a musician, he noticed that in this world, they were pursing each other the most. He realized that if Akihiko is around, he won’t be able to be free with his music, that his very own existence meant fundamentally nothing but suffering for Akihiko, who had given up on playing the violin because of his feeling utterly overwhelmed by Ugetsu’s talent. So Ugetsu decides to break up with Akihiko, but even after the end of their love relationship they continue living together developing a toxic relationship of codependency. For these past two years, they’ve been hurting each other. In fact both Akihiko and Ugetsu have relationships with other partners, but at the same time they occasionally have sex together. Ugetsu himself admits that he is the worst with Akihiko but the other guy has not given up at all even after being turned down. Ugetsu has constantly been met with failure trying to push him away at every available chance. Even though Ugetsu still loves Akihiko and want to be with him, he has chosen his love for music over his love for Akihiko and he’s always waiting for the other to leave him.
Ugestu takes an interest in Mafuyu during his on-stage performance.