The Bond…!! (繋がり…!!, Tsunagari…!!) is chapter 229 of the Naruto manga.
Surprised by the demon fox's chakra, Sasuke asks Naruto what he is. Naruto responds that he is a friend. Naruto attacks and Sasuke is unable to keep up with his speed. Naruto begins beating sense into him, causing Sasuke to yell that Naruto, never having had a family, can't understand what it's like to lose them. Naruto admits that this is true, but says he had come to think of Sasuke as a brother. Realising that Naruto regards him with a familial bond, Sasuke's Sharingan fully develops. He puts on his Konohaforehead protector and promises to sever their bond so that Naruto will no longer pursue him.