Legend has it that the one bright haired woman will unlock the true power of the seal, just as hamura did. Strength great enough to break the very fabric of reality.
The seal is much more than a containment unit to store massive chakra, or to allow regeneration. It's an interdemenstional portal.
Sakura's been working on a jutsu to use that to her advantage. Created after studying tobi attacks,
"Tsunade-sama I will get Naruto and Sasuke back together"
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