The popular writer Shinobu Satou is the author exclusively of stories without a happy ending. Right now is trying to write, without success, a book with an happy ending, because many of his fans are tired of the classic bitter end. After a meeting with the editor and after missing the bus to go home due to a fan that want an autograph, he finds, near an abandoned building,a little girl on the sill of a window of the building. The latter, sitting in order to give the shoulders, wearing a backpack from the wings of an angel. Satou rushes inside the building, becoming a witness to a mortal fight that takes place under the eyes of Eri Makino, the girl on the sill.
From that moment on, all decided by Osamu Dazai (fake name), the fans that made him miss the bus, Satou's life takes a strange flap like in his books. Infact by this moment on he have to take an eye on Eri, like a bodyguard for those who want to hurt her. But it doesn't end here, right now Satou is taking part in a game, similar to snakes and ladders. The only way to clear the game is to eat cookies with Eri in a certain place, if that doesn't happen the world will end.