Alipede is an 'apostle' or high-level assassin in the Glory Organization, a killers' club under the guise of an orphanage. He was reputed to be very genius and ruthless, his strength when fighting was insane.

but even so, in this world god created man with his partner. And that's an absolute thing. All beings in this world have half of their souls. And if a person rejects his soul mate, then that soul mate will be hurt. Tormented either physically or mentally.

Then damn it, Alipede who is a 'high level killer' also certainly got his soul mate. Half his soul. A naive girl who is stupid and weak, also very clumsy. Every time Alipede rejects her, then the girl gets hurt.