Board Thread:Naruto Discussions/@comment-36221354-20180717114536/@comment-32685487-20180718050104

He bit off a piece of Hashirama's shoulder skin, and put it into his chest hole when he came back to life, the chest hole was where Hashirama stabbed him through the heart to kill him. The chakra can't be the only prerequisite or Naruto would have the Rinnegan and so would Obito(of his own)

https://2.bp.blogspot.com/-Ya7aP4Ucx0U/WCWcbRxLTRI/AAAAAAACl1s/nj6Yc4JVXL4pxxtqsSs6yWQfhYCDD0phQCHM/s16000/0681-014.png