Toaru Majutsu no Index - Volume 17, Chapter 4: The Sword that Brings War and Disaster. Sword_of_Mercy.

Two years ago, the mere fifteen-year-old scion of the Lin family, in front of the colossal behemoth that is the Murong clan, made a vow!Two years later, no one knows what he has gone through, but from the moment of his return, he radiates a brilliance that seems to compete with heaven and earth!(Note: The protagonist of this book is very aloof, cold, and passionate. Those who like to read about a military king's ambiguous romances and flirts, please bypass this one.)

The Fourth Shinobi World War is over. All enemies are defeated. Finally, a long peace reigned in all countries. The Seventh Hokage laid down his arms and lost all his Youth Power. One dream, the goal for which he spent his whole life, has been achieved. His path is over. Is this really the end? Could it end so easily? What if the Savior of this World turns into an arrogant and cunning ruler?Perhaps no one would ever have been able to predict such a result. On that day, everything changed ... Countries, riches and power, the most beautiful women and their young daughters - he will subdue them all! The Seventh Hokage with the strength capable of conquering the heavens chose a different path, now he will take everything for himself and pave the way to absolute world domination!

After waking up in the body of the Young Master of the Luo family, he finds he has the knowledge of hundreds of games and Light Novels. However, he finds his Dantian is crippled, so he can’t practice cultivation! Luckily, he has the Upgrade system.

Zhou Yu was ordered to enter the city and get married. Even though my wife didn't like me, my father-in-law disapproved of me, my colleagues always wanted to bully me, and the bad guys were always looking to take me down, but touch me, that's fine, touch my wife, that's not. Whoever lays a hand on her, I'll take down. I fought until the whole world bowed down, then returned to the village with my wife in glory!