Muno to Sagesumareta Kizoku no Kunan wa Saikyō e Itaru Mo, Sono Jikaku ga Nai Mama Musō suru

Radi, the ninth son of a powerful noble family, possesses a useless skill that only improves his eyesight, and is considered incompetent by those around him. While venturing into a dungeon to rescue a cat he befriended by chance, he encounters the boss and finds himself in a life-or-death situation. Using a magical item that separates mind and body, Radi is sealed away along with the boss, an evil god. Unable to die within the mental world, he is repeatedly killed by the evil god, and as a result, his previously useless skill awakens. Realizing he can copy the magic and skills of anyone he sees, Radi gains the evil god's power and breaks the seal. However, hundreds of years have passed since his return, and Radi, still believing himself incompetent, has no idea he has become the strongest...!