While it's true that Naruto can access Kurama's chakra and power, he doesn't "go one-tailed fox".
* Naruto first learns to control Kurama's chakra in Episode 135 of the anime. This is during the Chunin Exams arc, after he faces off against Sasuke and becomes overwhelmed by anger and despair.
* The first time Naruto fully unlocks Kurama's power is during the Pain arc, around episode 151. This is a significant event in the series, as Naruto learns to control Kurama's chakra and uses it to fight Pain.
However, it's important to note that Naruto doesn't transform into a single-tailed fox. He can access different levels of Kurama's chakra and strength, and his transformations involve different appearances and power levels.