Level 0 no Maou-sama, Isekai de Boukensha o Hajimemasu

In a world beyond his own, the once invincible Demon Lord Ishuto was defeated by a group of heroes and reincarnated as a young man, retaining his formidable powers. Undeterred, Ishuto resolved to establish a new dominance in this unfamiliar realm. He entered the adventurer training school, where he was taken under the wing of the elite adventurer Airis, who recognized his exceptional strength. Due to his extraordinary abilities, Ishuto graduated from the program on the very first day, earning the unprecedented title of "Level 0" – a distinction reserved for those who possess abilities unmatched by others in the world. As a maverick Demon Lord, Ishuto now navigates this new world with unparalleled power, defying the norms and forging his own path.