The moment he saw the flesh and blood, Toji had already seen through Tobirama's plan.
Tobirama...
Even the wisest could make mistakes. He had left behind this piece of flesh as a contingency. Even if he truly died unexpectedly one day, Toji could use Impure World Reincarnation to bring him back.
This had been part of their original agreement, a secret between the two of them. Other than Tobirama, no one knew that Toji could use Impure World Reincarnation as well. Their enemies would think that killing Tobirama meant everything was settled.
Even the Reanimated Ninja used for the speech before Shadow Spirit Hall had been prepared with Tobirama's help.
Over the past few days, neither Senju Touka nor Hiruzen Sarutobi had come to him about this matter, which further confirmed that Tobirama had kept his secret.
The problem was that it was a secret.
The second half of that saying was: even the wisest could make a mistake.
It reminded Toji of a particularly classic scene—
[By using Agul's energy to reverse Gaia's Heavy Particle, Gaia could be turned into Antimatter Ultraman. The two human hosts agreed that once the trouble was resolved, Agul would fire a beam at Gaia and return Gaia to normal.]
They were likewise comrades who fought side by side. Likewise, if one side refused to act, the other would "die"—Tobirama's current situation was just like Gaia, the Will of Earth from another dimension.
As long as Toji refused to fire the "Will of Fire" beam, Tobirama would remain trapped in the Pure Land forever.
Would Toji act as Tobirama wished?
The answer was obvious. "Fire Release: Flame Technique."
Toji formed the hand seals with one hand, and a tiny cluster of flame drifted from his mouth, precisely burning that piece of flesh to ashes.