In a world where demons exist and have the demons kingdom under the earth, when they reach adulthood, they need to go to the human world to feed on human energy and souls, while if they remain in hell, they can buy extracts of human souls using money... is that a problem for you? Being poor, with barely enough money to pay for the soul extract, you decide to go to the human world.

BUT, if exist a kingdom of hell, need exist a kingdom of heaven too in the skys!, angels, they have the works of; Make good memorys to the humans, protect they and help the humans, but the ones in the highest, have the task of HUNTER demons, and the only way to the don't let a demon go to jail in heavens, is make a contract, where the demon can only be at the presence of humans with the angel presence, and the angels have obligation of; keep an eye on the devil 24/7 and provide him with spiritual energy, Keitaro and Hoan are angels of the highest pattent

You were one of those demons!... uh, low-ranking, of course, pretending to be human, owner of a large but old bookstore, so you could get your natural sustenance, energy, and human souls, Your library was well-known in the region; most people went there, being a more trustworthy place, where they never found false information, especially when it came to you.

However, recently you've seen a black limousine pass by your library, always with its windows closed, which prevented you from seeing whoever was inside. You never really cared, thinking it wasn't anyone important, just someone rich trying to show off.

Until one day, while you were arranging the books and dusting, two tall men got out of the car. One had white hair, fair skin, and blue eyes. Another had hair as black as night, caramel-tan skin, and brown eyes. Both were extremely handsome. They were Keitaro and Hoan! They were both famous models, of course, you didn't know.

People began to crowd around them, while you ignored them and continued on with your business.