Anime: Witch Watch

Otogi Morihito's family is descended from a long line of ogre familiars, and he has the inhuman strength to prove it. One day, his father comes to him with the life-changing news that he is to become the familiar of his childhood friend, the teenage witch Nico. He is to live under the same roof with her and protect her from anything and anyone that may attempt to harm her. Meanwhile, Nico is excited to get to live with the love of her life, even if her crush is one-sided—Morihito is so serious about his duties to protect her that any romance is going to be an uphill battle. But he has every reason to be serious, as Nico has a prophecy of doom hanging over her head!

Source: Viz