The Heavenly Demon Doesn't Want to Level Up

"Goryeo prince Jin Yuseong, a martial arts hero, seeks a new beginning after the loss of his comrades leaves him feeling isolated. He steps through a magical palace gate and finds himself in modern-day Seoul, where he inadvertently becomes a hero during a gate break mission. This act draws the attention of Safe Gate, an organization dedicated to protecting civilians from threats emerging from these gates. Desperate to avoid being recruited by Safe Gate, Yuseong assumes the identity of a high school student, pretending to be the nephew of a former comrade. But can this disguise truly help him escape his past as a fighter? Original Webtoon: KakaoPage, Daum. Official Translations: English, Japanese."