Morihito Otogi, a high school student descended from a lineage of monsters, lives a peaceful and normal life until his childhood friend Nico moves into his house. Nico is a witch in training and she chooses Morihito as her familiar. Nico is delighted to be reunited with her old friend and her lover, and Morihito is tasked with the dangerous task of protecting her from a predicted disaster. Between the unexpected chaos caused by Nico’s magic and the inconvenience of sharing a home, their lives become a whirlwind of mischief and mysterious threats.