Game Master

From Line Webtoon:
"Gamemaster," a high school streamer, dedicated his life to beating the supposedly unbeatable game "Hero's Destiny." Finally succeeding after ten years, the realization that he's wasted his life is short-lived, as the game asks him to keep playing. Only for him to wake up inside the game after he agrees, in the body of Callix Szcecin, the meek young son of a count. Together with Lyla, the maid and assassin hired by his stepmother who failed to kill him, Russel, the loyal knight, and Kraut, a young knight with much potential, Callix must survive the game again, in person.