Watch full Itsuka Tenma no Kuro Usagi Episode 13 (OVA) English Subbed online for free in HD. Full HD Itsuka Tenma no Kuro Usagi Episode 13 (OVA) English sub streaming online. A Dark Rabbit Has Seven Lives. 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.