The protagonist starts out a little invincible, then becomes completely invincible later. A semi-harem. Carefully researched, with a seamless timeline.
When was Konoha at its most glorious?
Was it when Hashirama Senju and Madara Uchiha were inseparable?
No. It was under the rule of Uchiha Nobunaga's New Konoha.
The Uchiha Clan was never wiped out, Danzo died early, Itachi never went insane, and Sasuke and Naruto grew up surrounded by love.
Uchiha Nobunaga transmigrates into the world of Naruto. Although he has never watched Naruto, he did study the much harder subject of functions. He picks up ninjutsu at a glance and masters it in no time, becoming one of Konoha's famed duo with Minato Namikaze, feared throughout the ninja world.
When Kushina goes into labor, Minato sends Uchiha Nobunaga to explain things to the other nations. After completing the mission, he goes to Tanzaku Town to fulfill his old promise to Tsunade.
Then comes the terrible news: Minato and his wife have died in battle. Uchiha Nobunaga backs Tsunade as the Fifth Hokage, and together they carry out the reforms Minato had dreamed of. He secretly investigates the cause of Minato's death, looks after Naruto Uzumaki, gives Naruto a warm and loving childhood, and instills sound values in the Uchiha Clan. After eliminating Konoha's underground forces, he begins studying the First Emperor's philosophy of unification.
He fights Obito and Madara, takes on Kaguya and Isshiki. Those Otsutsuki think they can do as they please? Around here, I make the rules.