Adamantine Sealing Chains was a secret sealing jutsu passed down through the Uzumaki Clan, and only members of the clan could use it.
Even Minato Namikaze and the Third Hokage, who had learned every Uzumaki Clan technique, knew nothing about this jutsu.
They had even once believed Adamantine Sealing Chains was a kekkei genkai. Only after Kushina was resurrected did she explain that it did indeed require Uzumaki blood to use, but differed from an ordinary kekkei genkai.
Even among the Uzumaki Clan, very few people could master this ability. In fact, it had nothing to do with the purity of one's bloodline; it depended more on the user's proficiency in sealing jutsu.
Ever since the Uzumaki Clan was wiped out, Kushina had been the only person who had mastered this jutsu.
Although members of the Uzumaki Clan could still awaken it on their own, without sufficient proficiency in sealing Jutsu, the power of their Adamantine Sealing Chains would be severely limited.
Awakening it spontaneously was also extremely rare. Naruto in his previous life, for example, had possessed Uzumaki blood, astonishing strength, and immense reserves of chakra.
Yet he had never awakened Adamantine Sealing Chains.
So, a few months earlier, Kushina had begun systematically organizing what she knew.
After compiling and organizing the Uzumaki Clan's most traditional methods, Kushina proposed having Naruto master Adamantine Sealing Chains through training.
That had been around the time Naruto and the others returned from the moon.
Kushina then found a suitable time to call Naruto and Karin over and teach them personally.
As for the Uzumaki Clan members still out there, Kushina had specifically asked the Nine-Tails about them.
She learned that, besides Nagato, the leader of the Akatsuki, there was also a woman named Honoka on Summoning Island in the Land of the