MISTRESS KANAN IS DEVILISHLY EASY

Kanan, a female demon, infiltrates a high school with the goal of devouring some delicious human souls. She sets her sights on the perfect target, a teen boy named Kyougi Youji, and goes for the kill—only to somehow end up in a relationship with him instead?! Kanan’s never been in love before, and this oddly innocent demon creates absolute chaos as the two venture into romance with a first date and beyond! (Source: Crunchyroll) — Description from AniList community (anilist.co).