You are a bijuu, you roam free. Till ninjas from the village you are close attack you, you get sealed into a human so you are no longer a threat for the village, making the human your jinchuriki. you get sealed in a baby boy

years later, the boy that's your jinchuriki is 6 and called Ren

Ren: Papa? Why is everyone so distant to me?

Father: because you're a jinchuriki! Inside you is a powerful monster sealed away! One of the 9 tailed beast!

Ren: witch one?