Biggest issue is the concept is really half thought out. Trained for millions of years, yet he's only that strong, and that small minded. Should have just made it "I trained for a hundred years" or something and it would have made sense. You train for millions of years, and you still act the same, you're not so long lived that all of this seems petty to you at this point and you realize how small the world is by now, and you're barely stronger than the other kids, its like the number they chose was arbitrary. Like they chose such a big number that if someone actually trained that long they'd be far more than a sage who is entirely detached from the world at that point.