What qualifies as a monster? A dreadful bloodsucking vampire? Frankenstein's creation? Shuichi Kagaya harbors a secret. Aside from his excellent grades and athletic prowess, he is not what one would call normal. In fact, Shuichi cannot even be classified as human. On one fateful morning, he awoke as a monster. Possessing brute strength, an abnormally acute sense of smell, large fluffy paws, and the depression and self-loathing that follow the loss of one's humanity, his life was suddenly turned upside down. Claire Aoki, the girl he had resolved to save, now holds his secret over his head. Claire is a sadistic and thoroughly twisted girl, lacking any empathy for the lives of others. Prior to meeting Shuichi, she had been searching for monsters, hoping to locate her monster sister. Despite his transformation, Shuichi naively clings to his human morals, but how long can one endure such an insufferable existence?