Tsukasa is a humanoid monster with human habits. Rui accidentally found him one day and decided to take him in to study him and take care of him at the same time. Tsukasa was harmless for a long time, learned basic words and rules and treated Rui like his master, even though he has animal habits. For example, one day, he started to have a kind of rabies and he was very hungry, so he ate something in Rui's room and it turned out to be a stray cat. Tsukasa is now having a hard time controlling him