To spend quality time with the girl he likes and lead a contented life is Denji's simple and ordinary dream. This, however, is far from the truth because Denji's fate is to be made to kill demons by the gang in order to settle his enormous debt. Turning his pet demon Pochita into a weapon, Denji will use any means necessary to make money. Unfortunately, the demon who had a deal with the gang killed him because he was no longer needed. Pochita, in a shocking turn of events, fuses with Denji's corpse and grants him the abilities of a chainsaw demon. The revived Denji uses his newfound abilities to swiftly and mercilessly eliminate his enemies. Denji gains the ability to transform certain parts of his body into a chainsaw. When the official witcher arrived on the scene, this attracted his attention, and the witcher hired Denji to work as one of them in the Public Security Bureau. Denji now has a strategy for defeating any foe, no matter how formidable, and he will go to any lengths to fulfill his simple teenage dream.