Of all the tailed beast Kurama was the most powerful among them. Kurama was the one who nearly look alike of the ten tails.

Before the sage of six path died he split up his chakra and used his "creation of all things" to create a nine seperate construct of living chakra and everyone of them has its name and the sage told them that they would be always together even they are seperated and someday they will become one again and find what the true power is.


Tailed beasts and the sage of six path


Kurama crying in front of the sage

At first Kurama used to hate and do not trust people because he believed  that his power will be used for their own will and purpose. The very first person he used to hate so much was Uchiha Madara because he was used for his own purpose. Madara also told him that the only reason why they are created was to serve the uchiha.


Kurama attacked Konoha under the genjutsu of Uchiha Madara

In order to preserve his life Kurama need to give some of his chakra to Naruto in times of danger situations.

Many times Kurama tempted Naruto to release the seal but Naruto managed to fight his temptation. But during his battle with pain when Naruto about to release the seal of the nine tails demon fox inside of him his father Minato "fourth Hokage" stopped him.


Kurama tempting naruto


Kurama first appearance in naruto

For a long period of time they are together Kurama used to watch the growth of naruto and he knew who naruto was. Naruto said to him that someday he will do something about his hatred.

During his battle with Tobi,  Naruto proved to Kurama through his action that he will help not only him but also the other tailed beast. In that way Kurama begin to like naruto and he let naruto used his power not as a weapon but as a partner and then Naruto open the seal of the nine tails and with their combination for the very first time naruto performed his biju mode and help the remaining beast under the control of Tobi. But since that was the first transformation of naruto it is far away from perfect and could only last for five minutes Naruto said that five minutes was enough to do something for the tailed beast particularly in pulling out the the rod which connect the beast from the control of Tobi and Naruto managed to pull it out.


naruto meld his chakra to Kurama before he released Kurama

Naruto released Kurama


Naruto in biju transformation