Mahiro Yasaka who was living a quiet life is chased by a wicked alien when the Nyarlathotep in the form of a silver-haired girl saved him. Explaining her lineage and the universe of H. P. Lovecraft, she declares herself to be Mahiro's protector, since aliens including Nyarlathotep find him and the Earth strangely attractive, for entertainment, auction or slavery, and she forcefully moves into his home. He gets more than he bargained for. When things couldn't get bothersome for Mahiro, Nyarlathotep transfers to his school under the name "Nyaruko Yasaka" acting as his relative and his wife.