There was a Cute Girl in the Hero’s Party, so I Tried Confessing to Her | Official Trailer

Yoki was once a human but reincarnated into a demon. He now holds a middling position serving the Demon King tasked with taking down the hero party. When he finally faces them, Yoki thinks, "No way… she's perfect." He falls in love at first sight with Cecilia, the priest of the hero party, whose serious gaze and every little gesture are too cute. She is an angel. Yoki decides to confess his feelings to her, beginning a pure isekai rom‑com fantasy between a human and a demon.