The story centers around Nyarlko, a formless Cthulhu deity who can take on the shape of anyone it wishes, but particularly the shape of a seemingly ordinary silver-haired girl. Mahiro Yasaka is a normal high school student who is chased by aliens one night, until Nyarlko saves him. (Source: ANN)

A new OVA of the light novel Haiyore! Nyaruko-san, titled Haiyore! Nyaruko-san F, has been green-lit. (Source: MAL News)

Animated Flash shorts based on the light novel series Haiyore! Nyaruko-san. In these shorts, Nyarlko, an anthropomorphized female version of Nyarlathotep from the Cthulhu Mythos, is constantly being told off by Mahiro, a normal human boy, for all the crazy or stupid things she does. In one of the shorts, Nyarlko is drawing a cover design for a body pillow. It turns out that the pillow's subject is a half-dressed Mahiro in what appears to be a hot and heavy scene with Nyarlko. Naturally, Mahiro proceeds to stab Nyarlko in the hand with a fork and threatens to kill her if she releases the pillow design. Other shorts revolve around various gags and occasionally feature Cthuko, an anthropomorphized female version of Cthugha, who's madly in love with Nyarlko.

Mahiro Yasaka is just an ordinary high school student, until one day he is suddenly attacked by a dangerous monster. Just when everything seems to be lost, he is saved by a silver-haired girl named Nyaruko, who claims to be the shape-shifting deity Nyarlathotep from horror author H. P. Lovecraft's Cthulhu Mythos, sent by the Space Defense Agency to Earth. She explains to Mahiro that the creature chasing him was an alien called Nightgaunt, who had planned on abducting and selling him as a slave. After rescuing him from the alien, the Lovecraftian deity falls madly in love with Mahiro and forces herself into his household, much to his chagrin. Moreover, they are soon joined by two others from the fictional universe: Cthuko, a girl obsessed with Nyaruko, and Hasuta, a young boy easily mistaken for a beautiful female. Together, the three eccentric aliens protect Mahiro from the various extraterrestrial dangers that threaten both his and Earth's well-being, all the while making his life a living hell.