Hmm...I don't think hes a genius as far as this Manga goes. I believe it's the fruits of his labor...his hard work. Idk.....I guess some may see him as a genius.
This
He didnt just watch jiriya and learn rasengan.
He busted his butt to learn it.
He didnt just summon gamabunta on his first try. He had many failures and he busted his butt to learn it.
He is indeed a natural genius.... of hard work.
He accomplished very difficult things, in spite of the slight handicap the nine tails gave him.
People tend to just forget that everything naruto has, he worked his butt off to get. Noting has changed from part 1 to part 2(in terms of how naruto gets powerups....through hard work)
Sage mode. He trained his butt off, and was able to manage the fatigue of basically 3 people(as shadow clones fatigue tranfers back to original) and train for a week straight. Instead of sleeping, he FURTHER trained at night(practicing rasenshuriken).
Rasenshuriken. He managed to take the mental strain of hundreds of clones, for many days, and not give up on learning futon.
Kcm. This is where the culmination of all his previous hard work was put to the test. He had to beat kurama in order to get the power.
Bm. This is literally the entire culmination of all his life put to the test. The only reason he was able to become friends with kurama, was because kurama knew the value of narutos word. He knew naruto doesnt ever give up. It took naruto 16+ years of work to get to this point.