Start with the Mangekyo Sharingan: Follow Lord Madara out of Konoha - Chapter 55: Three Tsunderes

A boy from 21st century Earth, met an accident and later was reborn in Naruto’s Ninja World.
He is born in Uchiha Family and becomes the useless brother of Itachi Uchiha and Sasuke Uchiha…. Let’s see how he changed the Naruto world.

- Description from Novelupdates

In a world where Classes, Stats, and Levels are the everyday norm, Reivyn has a secret.He was unusually aware of his surroundings from an incredibly early age, and Skills and Stats were acquired easily. He was just the son of an ordinary village family, and nothing appeared out of the ordinary on the surface. But below the surface, dreams of another life help shape his mentality and growth. Why does he have some remembrance of a past life, and what is his purpose in this new one?“Soul of the Warrior” is what I call a Semi-Isekai LitRPG. I say “semi,” because Reivyn's past life is remembered like a dream, and very incomplete. It is still Isekai, though, as he remembers enough that it directly shapes his personality and his sense of self.The System that governs the world of “Soul of the Warrior” is a combination of modified versions from Selkie's “Beneath the Dragoneye Moons” and Kosnik4's “Magic Smithing.” I have changed enough of these Systems and combined them in a way that is unique that I'm mostly sure it's fine, but I still have requested permission to use these ideas. They have both graciously granted me permission.Winner of the April Writathon Challenge.

A millennium had passed, and everything had lost its meaning in his eyes. Many heroes emerged from generation to generation, but he stood the test of time. That was his life, waiting for someone to come along and defeat him, but no one did. Nobody dared. Nobody tried.How can he allow this to happen? With the aid of his magic, he rose from his throne and set out into another world in search of excitement and, perhaps, a worthwhile adventure.What would happen if this last boss decided to venture into the human world for fun?

WARNING[R18]“Right now,” Zamian whispered, his voice low and sultry, “I'll make sure you only call my name.”“Z-Zamian, what are you... what are you doing?” she gasped as he pulled her even closer, their bodies fitting together perfectly. She could feel the warmth radiating from him, a magnetic force drawing her in.“Shh,” he whispered against her ear, his breath warm and tantalizing. “Not yet. Save that voice for later.”****Mira Adams, a 19-year-old girl, ran into the forest to escape the death that the war had brought her. Little did she know, she would meet Zamian Zan, a mysterious stranger who took her in for reasons unknown. She escaped the next day.On her 21st birthday, she finally left the small village after pleading with her grandfather, who agreed for reasons she didn’t understand. Little did she know, she was destined to marry the stranger she had met two years earlier.Zamian, now 23, is a CEO and secretly the king of a hidden kingdom. He marries Mira due to a debt her late father owed him, but that wasn't his only reason—he told her he wanted a child from her, though his true motives remain a mystery to her.