Utakata sensed that the thing inside his body had begun to leave him, and his chakra started to fluctuate violently.
These fluctuations made extracting the Tailed Beast Chakra much smoother. Tailed Beast Chakra had originally been something foreign, though the Jinchūriki's body had fused with it to a certain extent.
Under normal circumstances, the body's instinctive reaction would have been negligible. But at this critical moment, that instinct became the last straw that broke the camel's back.
Uchiha Shunichi was delighted to discover that the extraction of the Tailed Beast Chakra was becoming increasingly smooth. It struck him as strange, but before he could think further, he quickly split his attention and began suppressing the Six-Tails, which had already been sealed into a scroll-like container.
To Tailed Beasts, chakra and flesh were one and the same. That was why they could be sealed inside human bodies, but whether they were sealed away or extracted, it was an intensely painful experience for them.
Thus, when most of the Tailed Beast Chakra had been sealed into the container Uchiha Shunichi had made, it instinctively began to resist.
Because the Tailed Beast Chakra had not yet been completely sealed away, the Tailed Beast had no self-awareness at this point. Yet instinctive resistance was far more severe than conscious resistance.
Most Tailed Beast sealing attempts failed at this very step.
Uchiha Shunichi felt the pressure as well. Though he was indeed confident and quite skilled in Sealing Jutsu, his chakra reserves were still far inferior to those of a Tailed Beast.
So, Uchiha Shunichi activated Sage Mode. While using Sage Chakra to suppress the Six-Tails, he added Natural Energy and his own ocular power into the Six-Tails' chakra.
Going to such lengths to extract a Tailed Beast for Kirigakure was not merely to test