Sei is a very lazy God of Death. She would much rather spend her time eating sweets than collecting human souls. She has a particular affinity for human chocolate.

Sei is scolded by her parents because of her laziness. Her father tells her that if she does not collect one hundred human souls within a year they will kick her out of their home. What a disaster!

Sei immediately travels to a human world where she meets a prolific serial killer. She becomes friends with and makes a contract with the serial killer to collect the souls of his many victims.