Everything about this story don't make sense and is weird.
Coming out perfectly fine mentally after training for a millions year, Girls fall for him for no reason, somehow get possessed by someone. Somehow met someone that almost kill him after only 11 chapters. No matter what kind of genius someone could be, it would be impossible for a 10-20 years of a genius would compare to 1 millions years of even of the most slow learner possible.
There's other things that doesn't make sense, but this story might as well not exist without them lol
Bro you just explained the entire plot
His hair grew hella long and then when he turned back it went back to normal length... that's weird but ok