Umi no Yami, Tsuki no Kage (1987)

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: www.anisearch.com/manga/2818

Zwei Zwillingsschwestern kommen bei einem Ausflug mit merkwürdigen Bakterien in Kontakt und erhalten dadurch enorme Kräfte. Da beide denselben Mann lieben, versucht eines der Mädchen, die andere Schwester zu töten. Diese flieht mit ihrem Geliebten, während viele Unschuldige zum Opfer ihrer - mittlerweile wahnsinnigen - Schwester werden...

Quelle: www.anisearch.de/manga/2818