Doujio

Doujio is the manifestation of Doujinn's dream of becoming perfect.

Background
Doujinn did a lot of things to his body to create a perfect ninja, but in the process created a theory about the Rinnegan. Using one of his Truth Seeking Balls and a Chakra Receiver. He tried to stabilize his chakra into a new form, but caused the chakra to form a humanoid shape with a similar appearance. When Doujio first appeared, he informed Doujinn that he was perfection, and needed chakra to fulfill it. Doujinn realized if Doujio was kept the way he was, he would potentially become a problem for the ninja world. Using his unique sealing technique, he sealed Doujio into his brain so if that his chakra ever ran out completely or he was almost dead, then Doujio could be released with his thoughts and knowledge.