Haiyoru! Nyaruko-san OVA

The story of Haiyore! Nyaruko-san centers around Nyaruko, a formless Cthulhu deity of chaos (Nyarlathotep) who can take on the shape of a seemingly ordinary silver-haired girl. Mahiro Yasaka is a normal high school boy who is chased by aliens one night, until Nyaruko saves him.