Joushiki-shirazu no Saikyou Madoushi

In a world filled with monsters known as "labyrinths," Luke, who has been living alone in a labyrinth deep in the mountains, studies magic using a book left behind by his parents. He masters status magic, a requirement for admission to the Conqueror School (a training institution for those who can conquer labyrinths), and takes the exam, but fails the entrance exam. He is forced to become a "self-taught" conqueror, but despite starting from adversity, he overcomes various difficulties with his overwhelming ability and becomes the strongest adventurer.

(Source: Coamix, translated)