Darkness of the Sea, Shadow of the Moon is a oVA anime that premiered in fall 1989, produced by Visual 80.

About the production: the story comes from a manga, there are 3 episodes of about 30 minutes and its current status is "finished".

Its main genres are drama, horror and romance, with themes such as Twins, Shoujo and Love Triangle.

On AniList, Darkness of the Sea, Shadow of the Moon has an average score of 59%, an average score, and appears on 1,419 users' lists.

Lumi and Luka Kobayakawa are identical twins who both are members of the track team and have a crush on a handsome upperclassman Katsuyuki Tohma, but he chooses the latter. While Luka doesn't want to hurt Lumi's feelings, Lumi feels betrayed by her own sister. On their way to the party celebrating the graduation of eldest members of the team, they take shelter in a cave, which turns out to be a mass grave, and all members were killed by the strange smell from the cave, with Lumi and Luka only survivors. After the tragedy, Lumi has become a completely different person, and one day she literally emerges from the floor of Luka's room... (Source: Anime News Network)

Official synopsis from AniList.