Surviving a vampire assault, meeting various females troubled by strange forces, and simply attempting to get through life are some of the challenges Koyomi Araragi has faced recently. On top of that, he awakens one morning to find himself abducted and bound by his girlfriend, Hitagi Senjougahara. She has taken it upon herself to confine Araragi in order to keep him safe from Deishuu Kaiki, a swindler who duped Senjougahara's family. However, when Araragi receives a distressed message from his sister Karen, he discovers that the scam has targeted her.