Soushi is a high school student and a piano prodigy. He is forced to accompany Subaru, a transfer student who suddenly joins his one-person piano club wanting to play the piano, and ends up looking after Subaru for a piano duet. The two, who are similar in many ways, quickly become friends. On the way home, Soushi confides in Subaru that his father, who is under suspicion of embezzlement, will be coming to his recital in a month. However, Subaru doesn't seem to mind and instead encourages Soushi. Subaru leaves town alone and disappears into "Hotel in Humans," a hotel exclusively for assassins.