Changing jobs to be a [lock] at the Royal Magic Library

On the night she says goodbye to her first man, 26 year-old librarian Mizuki wanders into a mysterious library protected by magic and forest. Scouted by a librarian at the library, Mizuki ends up signing a contract with the help of his drunken energy. Her mission is to find her 'key' man among a gentle blonde prince, a dodgy magician, and a serious priest, and to rescue former librarian Ky Jay, who has been cast a petrifying spell. To do that, he says, he'll have to get in touch with the key men. And besides, the knight guarding the library also got involved with Mizuki so much ...