What sets a creature apart as a monster? Is it the blood-lusting vampire or the beastly result of Frankenstein's experiment? Shuichi Kagaya harbors a secret that defies conventional understanding- despite his exemplary academic record and athletic abilities, he is no longer human.
One morning, Shuichi awakens with heightened senses, muscular strength, fluffy paws, and a profound sense of sorrow that accompanies a loss of humanity. His life quickly dissolves into disorder. Claire Aoki, whom he had saved earlier, uses his transformation as leverage. Claire takes delight in inflicting harm on others, having no sympathy for their welfare. Before meeting Shuichi, she was scouring for monsters with the hope of finding her own flesh-and-blood monster sister.
In spite of being transformed into a monster, Shuichi tries to maintain his human ethics. However, how long can he persist in upholding his values in the face of such excruciating existence?
