The greatest value of the Eternal Mangekyō Sharingan was not that it spared Uchiha Shunichi the risk of blindness, but that it allowed his Mangekyō Sharingan to complete its evolution.
Because he had awakened his eyes too early, not only had Uchiha Shunichi's body suffered, but his Mangekyō Sharingan had also remained incomplete.
Back then, he had not even been able to deactivate his Mangekyō Sharingan. Those eyes had felt as though they belonged to someone else, constantly draining his chakra.
Before awakening the Eternal Mangekyō Sharingan, Uchiha Shunichi had believed this was a consequence of his transmigration.
But after his attempt to perform Impure World Reincarnation on his own flesh failed, Uchiha Shunichi concluded that he had merged with the body's original owner and gave little further thought to his Sharingan.
Only now, when his Mangekyō Sharingan evolved into the Eternal Mangekyō Sharingan, did Uchiha Shunichi realize that his Sharingan had never fully evolved, and that was what had caused the problem.
Now, Uchiha Shunichi fully understood his Mangekyō Sharingan's Dōjutsu, as well as the risks he had to bear when using them.
His Sharingan's Dōjutsu were simple: they controlled time. One application controlled his own time, while the other controlled all time.
As the saying went, those who toyed with time would eventually be toyed with by time. Uchiha Shunichi's Dōjutsu were no exception. Every use threw his timeline a little further into disarray.
Once Uchiha Shunichi's own timeline fell completely out of sync with the Shinobi World, he would disappear from this world.
Uchiha Shunichi could already feel fluctuations beginning in his timeline. Once those fluctuations reached a certain threshold, he would be affected.
As for what that effect would be, Uchiha Shunichi did not know.
He might transmigrate again, vanish completely, or drift outside the timeline