Concerning the chakra chains, I was wondering whether the technique was a Kekke Genkai or simply a Hidden Jutsu of the Uzumaki.
It's obvious that this technique is exclusive to Uzumakis but if it were simply a hidden technique (like the Nara's Shadow possession or Akimichi expansion jutsu) then anyone would be able to learn it; like how Minato learned Hidden Sealing jutsu of the Uzumaki from Kushina.
I'm thinking it's a Kekke Genkai, only because if the Uzumaki were wiped out, there'd be no one to teach it to Karin. However, as a bloodline limit, she could have well discovered it by herself, like Haku did in part 1.
What do you all think?