This is District A, somewhere in Asia, where skyscrapers and slums coexist in a chaotic mix.
Sakaki Takeru, who grew up in such a place, is scouted by an underworld organization's assassin squad and, under the guise of recruit training, becomes partners with Atonashi Isagi.
Upon their first meeting, Takeru fell for Isagi's looks, gentle personality, and the fact that he's still a virgin.
As a perfect match both professionally and physically, they seemed to be off to a smooth start.
Until "something" happened that provoked Isagi's wrath...