Actually, Shin Uchiha had wondered about this back in his previous life.
After all, the number written on the third coffin was four.
But just as that coffin was about to rise, Hiruzen Sarutobi had forced it back down, leaving the mystery unresolved.
Judging by the first two coffins, the fourth coffin was most likely supposed to contain the Fourth Hokage, Minato Namikaze.
But Shin Uchiha also knew that because Minato Namikaze had used the forbidden technique-Reaper Death Seal-his soul was now inside the Grim Reaper's stomach, effectively sealed away. Even the Impure World Reincarnation Jutsu could not summon him.
That was precisely why, when Orochimaru summoned the third coffin, the question of whether the Third Hokage had forced it back down,
or whether the summoning had failed because it could not reach the Fourth Hokage Minato Namikaze's soul, remained an unresolved mystery.
So when Shin Uchiha saw the Third Hokage raise that huge staff to force the third coffin down, he quietly interfered, causing the Third Hokage's attack to veer off course.
That single lapse was enough for the third coffin Orochimaru had summoned to emerge completely.
At the sight, Orochimaru's lips curled into a cold smile, and he said disdainfully:
"Teacher, you really have grown old. To think you could miss even an attack like that. Allow me to send you to the Pure Land myself."
With that, Orochimaru pressed his palms tightly together and shouted:
"Impure World Reincarnation Jutsu, open!"
The Third Hokage had no time to stop Orochimaru. Watching his movements, he clutched the staff tightly, his expression a mixture of pain and anticipation.
At Orochimaru's shout, the three coffins before him opened.
First Hashirama Senju.
Second Tobirama Senju.
Fourth Kazekage Rasa.
When the Third Hokage's gaze reached the third coffin, it lingered for a moment.