In this world there exists monsters, human emotions manifested into objects that create creatures made to kill everything in their way. One day, a boy's drawing becomes a monster, but instead of killing humans, it seems it wants to protect them?! This monster can think, feel, and look like a human, unlike other monsters. The boy who made the drawing became its mentor, teaching it human culture and becoming its only friend. That is, until one day, the boy gets killed by another powerful monster. This is the story of a monster learning and experiencing humans and their world on a quest for revenge against the thing that took his only friend away.