Board Thread:Theories and Speculation/@comment-33005792-20170901151707/@comment-734582-20170905125845

Elveonora wrote: I wonder how close my prediction will turn out being to the truth. Maybe i'm reading this wrong, but does the 4th databook suggest that Kaguya tried to make all Chakra her own before fighting her sons? Eventually, the "Rabbit Goddess" became known as a demon instead. And then, Kaguya became ruled by her desire to make all chakra her own.

To make all chakra one - Kaguya's desire eventually turned on Hagoromo and Hamura, her own twin sons with whom she had split her chakra. Kaguya formed a plan, and in order to take in all chakra, fused with the Shinju and battled against her twin sons. (p216-217).

Because it seems to support your idea that Kara was formed by Kaguya (to fight and unite chakra as her own. And with the seals, chakra given that way would always technically be her own).