When the Third Raikage first faced Kazemori Masaki, he noticed what set him apart from ordinary shinobi: his extraordinary ability to suppress his presence. Shinobi of the Third Raikage's caliber could easily do that while hiding, but suppressing one's presence until it was imperceptible even in battle was beyond most people. At the very least, the Third Raikage knew he could not do it himself.
As far as the Third Raikage knew, even the shinobi most skilled at concealing their presence in Kumogakure Ninja Village could not match Kazemori Masaki. That undoubtedly gave Masaki an advantage. In battles between shinobi, aside from predictions based on experience, the clues to an opponent's direction of attack came from the effects their movements produced. The more powerful the Ninjutsu, the stronger the chakra fluctuations it caused.
Yet with Kazemori Masaki's degree of concealment, it would be almost impossible to anticipate his movements once he attacked, unless he came close enough to trigger the body's instincts directly. A single glance had told the Third Raikage just how difficult his opponent would be to handle, and he could not help feeling a headache coming on.
Even in Konoha Ninja Village, only a handful of people knew that Kazemori Masaki had mastered the ability to control natural energy and could maintain Sage Mode as his normal state. This ability to suppress his presence was a skill possessed by those who had reached the sage realm. Cultivating sage arts was difficult in itself, and even information about successful practitioners had rarely circulated in the isolated shinobi world of the past. Thus, the Third Raikage had no way to recognize the true nature of this ability.
Just as the Third Raikage was inwardly growing wary, his opponent spoke. Kazemori Masaki wore a faint smile, as though addressing a