Story
Deimos no Hanayome: Ran no Kumikyoku revolves around high school girl, Minako Ifu, who has become the focus of the attentions of Deimos, former god of terror. For the forbidden love between him and his younger twin sister, Venus, the former goddess of love, he was turned into a demon by Zeus, and she was imprisoned in the Swamp of Death. In order to rescue Venus from her fatal punishment, he has to bring Minako, who appears to be her physical reincarnation, to the underworld so she can possess her body.
Synopsis via AniList (English).
