Kurama, also known as Nine-tailed Fox, or simply the Nine-Tails, is a major part of the Naruto series. Introduced in the very beginning as a monster fox that once ravaged Konoha, he was seen sealed inside a young Naruto Uzumaki by the 4th Hokage. From there onwards, Naruto's life changed dramatically because of this beast that he carried inside. He was ostracized, hated, and treated with contempt by everyone around him.
Eventually, he managed to conquer this beast just like he conquered every other obstacle in his path. He formed a great bond with him and turned this weakness of his into his biggest strength. Yet, he wasn't the only one to have this beast sealed inside him. Before Naruto, there have been several others who have harboured Kurama in their bodies. As such, he is one of the many Jinchuriki that Kurama has had over the years.
Kurama's Many Jinchuriki
Kurama was once a part of the 10 Tails that terrorized the world of Naruto. A beast known to swallow oceans and destroy lands, the 10 Tails brought on a cataclysm until it was eventually subdued by the Sage of Six Paths and his brother. Upon its defeat, the Sage of Six Paths became its Jinchuriki and on his deathbed, he decided to split the chakra of the Ten-Tails into nine parts, leading to the birth of the nine Tailed Beasts.
Kurama, the strongest of the nine Tailed Beasts, roamed lands for centuries without being subjugated to anyone, however, when powerful ninjas appeared, his power was used as a weapon. Consequently, he didn't trust humans, and thus every Jinchuriki that he had left a sour taste in his mouth. The very first Jinchuriki of Kurama was Mito Uzumaki, the wife of Hashirama Senju. After Madara used Kurama in his fight against the First Hokage, the latter decided to avoid having this catastrophe repeat in the future by having his wife become a Jinchuriki.
Years later, Kushina Uzumaki was brought from Uzushiogakure to become its second Jinchuriki as Mito was close to dying. Kushina remained the Jinchuriki of the beast for quite a while, however, just as with Mito, Kurama did not trust her. The beast itself was known to be a mass of hatred, so for him to trust humans was out of the question. Thankfully, Kushina was able to control his powers quite well due to all the love that was present in her life, thanks to Minato.
On the day of Naruto's birth, however, Obito Uchiha struck. The Nine-Tails was extracted from Kushina's body and let loose on the village. Together with Kushina's help, Minato was able to subdue the beast and eventually make his son, Naruto, its Jinchuriki. Interestingly, Minato only sealed half of the beast inside his son while the other half was sealed inside himself. As such, he was also a Jinchuriki of Kurama.
Naruto Uzumaki And Kurama
Having the beast who destroyed the village sealed inside him, Naruto's life was quite hard growing up. However, that certainly didn't stop him from achieving greatness. With a never say die attitude, he was able to turn Kurama into his biggest strength. Even before having full control over the beast, Naruto utilized his strength quite effectively in battle. Despite Kurama actually hurting him every time he summoned his power, Naruto eventually overcame the great hatred the beast bore in its heart with nothing but pure love.
As such, after fighting the beast and defeating it with his own power, he was able to access his chakra. It wasn't until much later in the war, when Naruto promised to help every single Tailed Beast and even went as far as learning their names, that Kurama was completely touched by him. The two formed an incredible bond that helped them save the world together.
Naruto's ability to touch the hearts of others with his kindness reached out to Kurama despite him being a mass of hatred. The beast went on to become a protector of Konoha as, for the first time, a human showed him the same love and care that the Sage of Six Paths once did. Thanks to Kurama, Naruto's strength shot through the roof and he was able to defeat the likes of Obito Uchiha, and even fight against Kaguya Otsutsuki. What's more, as an adult, Naruto was able to fight the likes of Momoshiki and even Isshiki.
Against the mightiest of all, that is, Isshiki Otsutsuki, Kurama sacrificed his power to give Naruto access to Baryon Mode. By burning every bit of his life, Kurama once again saved the world. Sadly, Naruto is no longer the Jinchuriki of Kurama and now has lost the beast who watched him grow before its very own eyes. Whether Kurama will somehow return in the future or not remains to be seen. Regardless, the effect that he had on Naruto and the series as a whole will always remain profound.