Sudo ostensibly works as a normal deliveryman but actually acts as a "courier" for the underworld, sleeps with his neighbor Uno after they got drunk over dinner. The next day, Uno becomes very distant from him. Worried about Uno's feelings for him, Sudo sees Uno being harassed by some thugs on the street, and he reflexively takes Uno by the hand and try to run away. Attacked by enemies, the wounded Sudo was saved by forming a contract bond with Uno, a descendant of witches, who has been hiding his powers in secret.

(Source: &.Emo, translated)