Kurama

Kurama is the Nine-Tailed Demon Fox, an ancient beast capable of immense destruction. Originally an antagonist, the fox was sealed inside Naruto Uzumaki by the Fourth Hokage, Minato Namikaze. This seal binds them together and allows Kurama to share its massive chakra with Naruto, though the connection remains imperfect. As their bond strengthens, the two become inextricably linked; if the seal breaks, both face certain death. Jiraiya remains a critical figure in this dynamic, possessing the ability to manipulate the seal's strength to ensure Naruto's survival.