Pain…!! (痛み…!!, Itami…!!) is chapter 129 of the original Naruto manga.
Naruto has difficulty recognising Gaara in his transformed state. When Sakura tells him who it is, Naruto remembers Gaara's claim that he is a monster and realises he wasn't exaggerating. Naruto suggests running, but Gaara takes his preoccupation to try and kill Sasuke. Sakura shields him, but Gaara immobilises her. Tormented about her selfless act, Gaara reflects on his childhood. When Gaara was a child in Sunagakure he only wanted friends. His peers feared him for being the host of Shukaku and ran when he was nearby, and he would accidentally attack them while trying to stop them. Sympathising with them, Gaara wondered what it was to feel pain.