ninetail demon and naruto

Naruto was not made aware of the Nine-Tails' presence within him until twelve years after its sealing. He first made use of its chakra during his battle with Haku. Believing Haku to have killed Sasuke, Naruto gave into his anger and entered his initial jinchūriki form in order to defeat Haku. He didn't realize that this was the Nine-Tails' chakra until he was later taught to take advantage of it by Jiraiya. To force Naruto to call upon the Nine-Tails' chakra, thus enabling him to use the Summoning Technique, Jiraiya threw Naruto off of a cliff. To save himself, Naruto entered his subconscious and met with the Nine-Tails for the first time. He demanded some of its chakra as "rent" in order to save them both, and the intrigued Nine-Tails complied, allowing Naruto to summon Gamabunta.
Naruto took advantage of the Nine-Tails again during his fights with Neji Hyuga and Gaara, requesting some of its chakra to help him with the battles. Later, when Kabuto Yakushi severed Naruto's heart muscles and the neighboring chakra system, the Nine-Tails was unable to heal the damage. It, like Naruto, had a near death experience, something it was slow to recognize. Naruto, and, through him, the Nine-Tails, were saved by Tsunade. During his battle with Sasuke at the Valley of the End, the Nine-Tails gave Naruto enough chakra to attain the one-tailed transformation, something the Nine-Tails indicated that he should be grateful for.