Humans or devils? One day, Tachibana Ritsuka, a student attending Shikou Academy, gets attacked by a group of mysterious men. From then on, Ritsuka gets targeted as she is the last key to locating the "Forbidden Grimoire". Getting allured and tempted by devils, her days change little by little. The plot takes the same direction as the anime's, with numerous endings awaiting this captivating tale. Who will you choose? Humans or devils?