Hashiba Sora has been in hospital since he fell from the school building. When he comes back to the boarding house, his childhood friend Fujimori Sunao transfers to the school. By the good office of Honjo Matsuri, who is the leader of the boarding house and their childhood friend, Sora and Sunao are assigned the same room. However, because Sora doesn't remember Sunao, Sunao gets angry. Then, Matsuri tells him that Sora has lost his memory