There Was a Cute Girl in the Hero’s Party, so I Tried Confessing to Her

Story:

Youki died in a traffic accident and is reborn in the fantasy world! However, instead of becoming a hero of legends, he turned into a super-powerful demon. With no desire to become a Demon Lord, he sits in the Demon Castle as a random low-ranking guard. One day the Hero's group storms the castle, and on a whim he knocks them all out. Having healed and preparing to send them back to the city, he notices the priestess and falls in love with her at first sight!