What does one consider to be a monster? A horrible bloodsucking vampire? Frankenstein's creation? Shuichi Kagaya has a secret. Other than having great grades and being skilled at sports, he isn’t what one would call normal. In fact, Shuichi cannot even be considered human.

One fateful morning, he woke up as a monster. With brute strength, an abnormally strong sense of smell, big fluffy paws, and the depression and self-hate that comes after losing one's humanity, his life was suddenly flipped upside down. Claire Aoki, the girl he had decided to save, now holds his secret over his head. Claire is a sadistic and utterly twisted girl, with no sense of empathy toward the lives of others. Before meeting Shuichi, she was in the search of monsters, hoping to find her monster sister. Despite becoming a monster, Shuichi naively continues to hold onto his human morals, but how long can one last in this insufferable way of living?