Yuusha Party ni Kawaii Ko ga Ita no de, Kokuhaku Shitemita.

Youki died in a traffic accident and was reborn in a fantasy world! However, instead of being the hero of legends, he ended up reincarnating into an overpowered demon. Having no desire to become the Demon Lord, he sits around in the Demon Lord's castle as a random low rank guardian. One day, the Hero's party comes to attack and on a whim he knocks out the entire hero party. Healing up the Hero party and then preparing to send them back to town, he notices the female priest and falls in love at first sight! (Source: Manga Mirai)