One day, Haruki Ito and his whole class are suddenly transported to another world. At the summoned destination, they are all imprisoned with one boy and one girl for every cell and through drugged food, are forced into a physical relationship. Haruki is paired with Shizuka Inoue, a girl who dresses rather plainly but is actually quite beautiful underneath her facade.

When they are later released from the prison, the girls are revealed to be enslaved and in order to ensure their safety, the boys must now help the country they were summoned to by exterminating monsters and fighting the forces of other enemy nations.

For Shizuka's sake, Haruki begins training and comes to realize he has been granted a divine power known as the "Ripper." This power, unparalleled in its might, sets him apart from the others as a force to be reckoned with. As he adjusts to his new life, Haruki discovers the true extent of his newfound ability.