OVA
After taking a nap, Mirai is thirsty and Gekkō refuses to buy her a drink. She notices a strange looking potion on the table and chugs it despite Yūichi previously telling her not to touch it. The potion causes the person who consumed it to swap souls (thus switching bodies) with anyone he or she comes in contact with. The main cast spend the day inadvertently swapping bodies due to Mirai's carelessness. This OVA episode was written by the author, Kagami Takaya himself. The episode consists of three short stories, two of which were created based on ideas tweeted in by fans, and one of which is a crossover with another of Kagami's work, The Legend of the Legendary Heroes. Note: Unaired 13th episode bundled with the limited edition of volume 9 of the original novel. (Anidb.net)