MTL - My Hero Academia: My Personality is the World - Chapter 8

One day, Luo Jian woke up from his sleep and found himself in a locked chamber where the door and window were all sealed. A note with a few lines written on it was tacked to the wall: “Escape from this room within an hour, otherwise, you will die.”

There is a sequel called Reincarnation Night (轮回之夜) that takes place in the same universe but has different main characters

- Description from Novelupdates

Medieval times, warring knights, dragons, demons, gods, pirates, behemoths...Barbaric, ignorant, backward, numb, starvation widespread, people unable to make a living...Damn it! Punch to explode this era!!Reclaiming wilderness, farming, bridge building, road paving, coal mining, excavating minerals!Leveling up, recruiting apostles, forging an army!Barrage troops! Pushing horizontally!Quack! My steel torrent is invincible in this world!!Roman: “I am your destiny! Kneel before me!”So, you were supposed to farm, but somehow you ended up establishing a vast empire and becoming the emperor?

A tale about the former leader of a special organization served under royalty, now leaving his past life behind and unintentionally getting involved with the martial world.

- Description from Novelupdates

Han Yun was spoiled from childhood.

He survived past his emperor dad and crown prince elder brother, and became an emperor.

He didn’t know how to govern the country, but he was lucky—there was a Grand Preceptor who “assisted” him, spoiling him even more than his father did.

After just a few years, this puppet emperor died. When he awakened, he had transmigrated into the modern world, becoming a third-rate model struggling alone without any loving parents.

Just when he thought he had become a little cabbage that nobody wanted and no one would ever spoil him again, a certain ancient monster of a Grand Preceptor who had lived 1,000 years appeared again… and looked to be doing quite well for himself.

The utterly impoverished little emperor had tears in his eyes: “Beloved subject! Zhen (royal We) have missed you so much!”

Grand Preceptor: “Your Majesty, this minister has waited for you for a thousand years.”

- Description from Novelupdates