Oosaka Jin moved to a new school because of his parent's job transfer. Rumour has it that some students from that school have gone missing recently. While trying to find the roof, he hears a voice calling for him and finds himself transported to a strange place. He is in a cave of some kind and in front of him is an altar with a sword in it. He feels nostalgic at the sword, even though he hasn't seen it before. When he holds the sword, it vanishes. Suddenly, he sees a white wolf in front of him. The wolf is a tsukigami spirit named Kouga and he has been sleeping for a long time. Their meeting is interrupted by some weird monsters which attacks them. They are saved by three students wearing the same uniform as Jin and finds out they have their own tsukigamis. These Tsukigamis can change from animal form to different weapon forms. He is asked to join them in a fight against an enemy tsukigami & his keeper (who may be linked to the missing students) and soon, Jin finds himself caught in an ancient fight between light and darkness that started 1500 years ago...