Every night when certain individuals close their eyes and start sleeping, they are pulled into a place called "The Personal Dimensions". During their stay there, they are capable of manipulating the contents of the dimension to their whim. However, evil creatures called Draugrs appear to prey on these humans, forcing them to defend themselves with the help of an entity to guide them.

The first month of his first year of high school, Klaus Weber encountered a conspicuous, blond middle school student Tsujihara J. Freda; however, she appears to know Klaus despite him having no memories of her.

Soon after the encounter, Klaus is discovered to have been "reincarnated" and is able to enter the Personal Dimensions, and to fight the Draugrs invading the place. Recruiting those who are reincarnated as well to find the truth as to why they were reincarnated, Klaus now has to balance his school life, his social life and his new dungeon-crawling life.