He used it during invasion of pain which was at least a month before due to and konoha rebuilding, armies mobilising and the summit happening, and the war as being going on for 3 days now. wasn't exactly a new powerup, Kurama explained he was the one that didn't want Naruto to use the Toad power since he had his.
Actually, i forgot all about tha.O_O however .that case was kinda of different in my opinion since naruto was totally unconsious of it and so learned nothing from it in my opinon.
I guess it would be unfair to call it an asspull powerup since it existed many chapters ago i guess. I retract my statement about it being asspull
Born as genius doesn't mean every power received is non-hard work. Everyone with Sharingan, Mokuton, Rinnegan, Bijuu etc, still had to train hardly in order to get more powerful with their power. It doesn't happen on its own.
I agree with everything except Sharingan , Rinnegan and Bijuu
Sharingan=
-Awakening-near death experience
-2-3 tomoe- overall power as a ninja grows , however you do not train it specifically
-Mangyekyo- Death of someone dear to awaken. Powers grows much greater with Hatred
-Eternal Mangyekyo Sharingan- Swapp eyes, tadah
Sharingan is basically a ad-hoc power based on your experiences. You don't need to train hard for the sharingan power. , you just had to meet certain criteria
Rinnegan=
What hard work do you need to do? You just needs to " Test your limits and break through" (Frozen quote lol)
Bijuu=
Level 1 = A bit of chakra ( Okay , this takes a bit of hard work )
Level 2= Maintaining sanity in face of tails sprouting ( Okay , this needs work too)
Level 3= Pull chakra out of Bijuu and take it's power. ( Okay , this needs effort)
Level 4= Work together with Bijuu to sync power or ask it to give you power. no strings attached ( No effort required )
One can simply jump to level 4 with no effort at all if one has the right character and mindset