Tokyo, year 35 Taisho era.

The organisation "Fuuma", established to maintain peace in the mortal realm, becomes aware of an aberration borne into the world. The evil god who once led a great army into battle with the holy gods but was thought to be defeated has revived once again. The identity of the reincarnated evil god's vessel is...

The protagonist Kitagawa Daisuke, an otherwise ordinary young man is abducted by a beautiful girl Kuroba Saya who then has sexual intercourse with him, which awakens Daisuke regarding his status as the evil god's incarnation as well as his abilities. Saya pleads with the awakened Daisuke to join her in crushing Fuuma, the holy god's shock troops. Now the millennia-old battle between light and darkness is about to reach a decisive conclusion

[Translated from Getchu.com]