The reason the "Uchiha Disappearance Incident" could not be used to truly punish Shimura Danzō was that he could not be convicted; legally speaking, there was insufficient evidence.
Who had given Koto the order? No one knew.
Where had the captured Uchiha ninja ultimately been taken? No one knew.
Koto was a ninja from the Root, so the conclusion that Danzō had given the order was correct?
A guess was only a guess, not concrete evidence—even if it was a reasonable one.
So if this matter were judged in a "court of law," Danzō would inevitably be found innocent.
But what if the Fourth Hokage used extrajudicial punishment? First, Danzō had a very high status and seniority. Second, internal affairs differed from external affairs; the important thing was to follow the rules. Third, the Fourth Hokage currently did not even have complete control over the Anbu.
To give the simplest example, if the Third and Fourth Hokage issued contradictory orders to the Anbu at the same time, whom should the Anbu obey? Theoretically, they should listen to the Fourth Hokage. But in reality?
So, the Uchiha ninja was currently classified as "missing."
Yuhara had once secretly followed Koto and discovered that he had entered an underground space. However, according to the subsequent investigation, that place belonged neither to the Root nor to the Anbu. Naturally, the Uchiha ninja was nowhere to be found.
Yuhara's actions in this matter had actually been somewhat inappropriate—or perhaps it would be more accurate to say that he had acted rather emotionally. He had realized there was something wrong with the mission only after the Uchiha ninja had been captured... If he had been willing, he could have tried to rescue the Uchiha on the spot.
But why should he save the Uchiha? If he