Tenjou Yuuya has been a bullied boy since the past.
He lives in the home of his beloved grandfather while he goes to school. As usual he receives a harsh bullying and he takes an extended absence from school to have some time to heal his wounds.
While on this long time of absence he takes the opportunity to clean his grandfatherβs house and goes to a room he never went before where his grandfather keep many different objects that he gathered from his travels around the world. While he was arranging the objects he found a door not on a wall among the objects.
Out of curiosity he opens this door what he found on the other side wasβ¦