Based on: "Valkyrie Chōkyō Semen Tank no Ikusa Otome 10-nin Shimai" (erotic game) by MBS Truth

The Valkyrie are charged with maintaining peace between the realm of gods, the realm of humans and the realm of the dead. The peace has started to breakdown and one of the Valkyrie has been possessed by a vengeful force.

(Source: Anime News Network)