rudeus from mushoku tensei jobless reincarnation using his healing magic to constantly heal his broken muscle fibers after every sword fighting spar with Paul his father and he constantly throws out almost all of his mana every night in his room and when it's morning he takes all of his mana back into his body. Also he's been doing that since he was a baby and he recreates all of the techniques for all three sword styles without any touki but with his pure body strength

Because it wasn't something that could be taught normally.


Chapter 126 - The Nameless Path