The story takes place in City Z, Japan, at a time when the world is teeming with mysterious monsters possessing terrifying powers, causing countless disasters. But it is also here that a superhero emerges, capable of single-handedly defeating and destroying these monsters. Because of this rare talent, many doubt his true abilities, and he never receives any trust from the people. The world's strongest superhero can kill anyone with a single blow. But nothing can challenge him, so he struggles with boredom and depression.