Mashle, magic and muscles. Volume 12, Mash Burnedead and the five siblings

"In the magic realm, magic is everything--everyone can use it, and one's skill determines their social status. Deep in the forest, oblivious to the ways of the world, lives Mash. Thanks to his daily training, he's become a fitness god. When Mash is discovered, he has no choice but to enroll in magic school, where he must beat the competition without revealing his secret--he can't use magic! Just as the battle with Doom and Mash is nearing its cli...