Inside the Aerial Fortress.
"Gelel Stone..."
Hyuga Kagami's gaze sharpened, then he suddenly understood.
He had been busy performing the First Hokage Cell implantation surgery on Karin and had not had the energy to keep constant watch over Neji. Only after he had finished did he learn about the Gelel Stone through the chakra he had left on Neji.
That was right. He had just completed the operation and successfully implanted First Hokage Cells into Karin.
The surgery had lasted intermittently for two or three days, involving seventeen implantations in total. By the end, not only Karin but even he, as an "Impure World body," was utterly exhausted.
Fortunately, after unrelenting effort, the First Hokage Cell implantation had ultimately succeeded.
From this procedure, Hyuga Kagami discovered that if the recipient possessed a sufficiently large chakra reserve, the success rate of the implantation would rise accordingly.
Nagato's success had not been due solely to factors such as the Rinnegan and the "Demonic Statue of the Outer Path." His enormous chakra reserves were likely also a crucial reason he had successfully fused with the First Hokage Cells.
Compared to Nagato, Karin was at a considerable disadvantage in this regard.
Karin's strength was not the sheer quantity of her chakra, but its quality and its special healing ability. Yet no matter how high the quality of her Yang Release chakra was, it could not surpass the Yang Release chakra within the First Hokage Cells, which contained the traits of the Divine Tree. Thus, when it came to fusing with the First Hokage Cells, there was a substantial gap between Karin and Nagato.
Under normal circumstances, such a gap could not be overcome.
Even with the assistance of a pair of Rinnegan, Karin's chances of successfully receiving the First Hokage Cells would have been