There was a Cute Girl in the Hero's Party so I Tried Confessing to Her.

Reincarnated as a mid-tier demon, Youki had one job: Crush the hero’s party. Then he saw the party’s priestess, Cecilia, and fell for her hard. Now this lovestruck demon vows to confess his feelings, even if it means betraying the Demon King. Will love bloom between these two sworn enemies? (Source: Crunchyroll)