Proof of Intentions!! (意志の証明!!, Ishi no Shōmei!!) is chapter 569 of the Naruto manga.
Son Gokū tells Naruto that it won't become his ally even if he saves it, unless it can trust Naruto, who is OK with that. Kurama ponders that it knows Naruto, and that nothing he can say will reach a tailed beast. Tobi pulls Son towards himself with chains intent on absorbing them both. B's still trying to make Son open its mouth and release Naruto. Naruto fails to make Son open its mouth, and decides using the Multiple Shadow Clone Technique to make Son puke him out, which it does. B celebrates it. Son tells Naruto that the chakra receiver in him slid from its chest to its neck because of the full tailed beast transformation. Naruto spots it, enters in his Nine-Tails Chakra Mode, and sets out to remove it, apologising to Son in advance if he needs to get rough. Naruto pulls himself towards the receiver. Tobi tries binding Naruto with the chains. Kurama recalls Naruto's past achievements, and thinks that if Naruto truly wants to help tailed beasts, that he should do like he always has and act. Naruto tries pulling out the chakra receiver, while a clone he left inside Son enters Sage Mode tries pushing it from the inside.