As each other's greatest enemies.
Tobirama understood Madara Uchiha as well as Madara understood Tobirama Senju.
Impure World Reincarnation had originally been a secret technique researched by Tobirama Senju.
It could be said that aside from Tobirama, Madara understood this technique better than anyone.
Even Black Zetsu did not know that the forbidden technique Impure World Reincarnation had an option called Impure World Reincarnation Release.
Seeing the white light rising from Madara's body and his expression, Black Zetsu, Obito, and the people of Kumogakure all scattered to either side.
Obito did not understand Impure World Reincarnation. He turned to Black Zetsu. "What's going on?"
Black Zetsu frowned as well. "I don't know either, but Madara seems to have lost control."
At that moment, White Zetsu, acting as a messenger, shouted at Black Zetsu.
"Lord Black Zetsu, Madara has broken free of control."
Black Zetsu's heart sank.
This is bad.
Seeing the surging hatred in Madara's eyes, Obito's scalp went numb as well.
"Wasn't Impure World Reincarnation your technique? You can't control him anymore?"
Black Zetsu had no idea why things had turned out this way, leaving him momentarily speechless.
With bone-deep hatred in his eyes, Madara said coldly,
"Though Impure World Reincarnation is a ninjutsu that summons the dead, Black Zetsu, unfortunately, I never told you that this technique has one and only one risk."
Black Zetsu had not expected to be outmaneuvered at a time like this. "What risk?"
"As long as the reincarnated dead know how to form hand seals, they can release the summoning contract of Impure World Reincarnation."
"Once it is released, the flaw of this technique immediately becomes apparent: an immortal body and limitless Chakra."
"They are no longer controlled by the caster and can act freely."
"I thought that since you were my inferior