Using the Soul Crystal Jade Marrow, Yechen completed Madara Uchiha and Hashirama Senju's evolution.
Neither man disappointed him. The instant their evolution was complete, they broke through that barrier and reached the immortal shadow level.
Upon reaching the immortal shadow level, Madara Uchiha's eternal Mangekyō Sharingan transformed into the Rinnegan once again, while Nagato's Rinnegan gradually disappeared, leaving him blind and eyeless.
As compensation, however, Madara Uchiha gave Nagato a pair of Three-Tomoe Sharingan from his treasured collection.
This would allow Nagato to live a little longer, too. After all, the Rinnegan's side effects had taken far too great a toll on him.
Of course, that would all come later.
Hashirama Senju also underwent tremendous changes upon reaching the immortal shadow level. He had evolved on the level of life itself. Standing there, he looked like a truly living person; if not for the fine lines on his face, no one would even have realized he was a body brought back through Impure World Reincarnation.
Once their evolution was complete, Madara Uchiha issued a challenge-not to Yechen, but to Hashirama Senju.
Others might not understand their friendship. Theirs was a love-hate relationship; otherwise, why would anyone call them a pair of "best bros"?
To prevent excessive destruction, Yechen allowed them to fight in the Training Grounds. Even if their battle shattered heaven and earth in there, not the slightest disturbance would reach the outside.
Since that was his personal cultivation space, he did not allow anyone else to watch. Only seven days later did Madara Uchiha and Hashirama Senju emerge from the Training Grounds.
Neither mentioned who had won or lost, but judging by their expressions, Hashirama had probably won again.
Otherwise, given Madara Uchiha's personality, he would never have been so calm. This also showed that Hashirama's control over