Novel info
Being A Mastermind At Naruto

Year 5 of the Konoha calendar.
Hashirama Senju and Madara Uchiha's battle at the Valley of the End ended.
In order to treat his brother's injury,
Tobirama Senju resurrected a medical ninja from ancient times, hoping that the other party could prevent his brother's injury from affecting his life span.
This medical ninja is called Shihara Emiya.