Board Thread:Theories and Speculation/@comment-30355627-20170210181343/@comment-734582-20170215230714

Lorenzo.r.1st wrote: actually, doned/gifted chakra can remain in people, if they used it for long enough. And here we run into the problem of poor terminology again.

First, Biju are actual spirits (or souls, if you want). Similar to the rules of Edo Tensei, a being possessed by a spirit can utilize that spirit's power. This is true for Jinchuriki and Edo Tensei and Transmigrants. Calling it chakra is confusing because it's a really far cry from the regular stuff people throw around. The Biju's chakra contains information on a person (equivalent to DNA). It seems that if you possess this spirit power long enough, the "DNA" rubs off on you and it becomes your own power. This can be seen in Gaara, in Hagoromo (who easily restored small pieces of chakra to biju), in Kinkaku and Ginkaku.

The second part is different: If you have a piece of implanted flesh for long enough, either the chakra or the flesh itself will eventually merge with your own. This is true for Nagato. However even kakashi became better and better at using the Sharingan, so it's possible this works for him too.

It's not that if you get some chakra, that can be assimilated: It has to be the "soul/information/DNA/essence" type.