Getsumen no Anubis

The protagonist (default name Keisuke) and heroine (default name Kaori) are astronauts living in a laboratory set on the moon. A group of American soldiers are also stationed there. Mysterious incidents begin to occur that threaten the lives of everyone there - there are multiple scenarios, but only one is explicitly horror-themed. Said scenario involves a race of mysterious space parasites that can take possession of anyone, leading the protagonist (and thus the player) to grow distrustful of the other characters.

[From endaso]