At this thought, the gaze of the Nine-Tails grew even more solemn. He could not figure out how Uchiha Chi had possibly discovered this. At the same time, he stared intently at the Uchiha Chi before him once again, and after a moment of silence, he feigned casualness and probed offhandedly, "Then, in your opinion, what is so extraordinary and unique about the two of them?"
"Extraordinary? They are beyond extraordinary! Since birth, both of them have naturally possessed a unique chakra fluctuation within their bodies. Although extremely faint, its essence is exceptionally powerful, and it gives a sense of boundless endurance.
Among them, the power that Sasuke possesses is the Yin Release, while Naruto has mastered the ability of the Yang Release. However, this fluctuation is extremely obscure and difficult to detect. Even someone of my great strength could only barely perceive it when entering a certain special state."
Chapter 366