"I side no one, japanese imperial demon army or vampire organization, both are my enemies" Garou saw himself in a new world, he wander around as he saw the devastated cities surrounded with Horsemen of Apocalypse, a monster that is threatening and controlled by a Seraphim.

Saitama transported in a new world different from his original world, naked in the cave he found a slime with human mind, they set their fate as the amazing duo not until a dragon was interested talking to them.

Saitama journey himself in becoming demon slayer, he is no longer one punch man, but he is one slash man, one slash from this hero and the demons are gone for good. THIS IS A PARODY, DON'T TAKE THIS STORY SERIOUSLY