Yuiko Kubozuka is a 17-year-old single high school student who loves animals; unfortunately, because of her overwhelming affection, they always run away from her. One stormy night, Yuiko accidentally scares her own cat up a tree, but a boy with fierce eyes and the looks of a wild animal helps save her cat and leaves without a word. The next day, the same boy turns out to be the new transfer student, Leo Aoi, whom everyone is frightened of due to his intimidating appearance. Regardless, Yuiko drums up the courage to thank him for last night. She soon finds out that underneath his frightening guise, Leo actually has a very sweet nature and also seems to have a way with animals, which makes her envious. However, Leo holds a dark secret: whenever he sees blood, he loses his human reasoning and unleashes his beastly instincts on those around him. Will Yuiko be able to tame the wild beast inside Leo or will he flee from her like all the other animals?