Deimos no Hanayome

Deimos was once a hansome god. He loved a beautiful goddess who returns his sentiments. The problem, well, she is his sister. For their crime against nature they were struck down out of Olympus. The brother is now a demon and the sister a rotting corpse at the bottom of the ocean. Deimos must choose between his sister and her living human incarnation. His sister is jealous. The girl is horrified and unsure of just what to make of her situation. A classic love triangle turned into a horror story.

(Source: ANN)

Deimos no Hanayome had seven volumes published in English as Bride of Deimos by ComicsOne from January 15, 2003 to April 5, 2004 before the publisher went defunct.