Rakuin no Monshou - Volume 11, Chapter 1: Rumblings

A teenager who unexpectedly gets transported to the modern world from ‘the world of the immortals’ . He finds himself in the body of an ordinary guy. He wants to go back to his world and for that, he will have to practice to get stronger and investigate the reason why and how he crossed through to this world.

The handsome Emperor falls in love with a Knightess! Knightess Poliana loses to the Acreian Army and despite her struggles to survive in a male infested military, she is now about to die. But then, the young king of Acreia sees her efforts and tells her: "I have a dream, I wish to conquer the world and become an Emperor, would you like to join me?"

This story is set during the end of the Sui Dynasty, a time where multiple powers struggled for supremacy and power.

Into the fray enters two orphans Kou Zhong and Xu Ziling; these two youths by many chances and luck obtain ‘The Secret to Long Life’ allowing the two to obtain profound martial abilities and a chance to rise to the top in this age of turmoil.

Wonder Woman: Why are you Superman’s younger brother? Eric replied: On the first day of travel, I, who was also a baby, climbed into Superman’s baby capsule, pushed him out, occupied the nest by myself, and became a “son of Krypton”.

Superman: Why don’t you save the plane? Eric replied: I will not lift things by stepping on the air.

Batman: Why didn’t kryptonite work for you this time? Eric replied: I originally wanted to get along with you as a Kryptonian, but in exchange it was alienation.

Okay, I’m not pretending anymore, I’ll showdown, I’m a native of the motherland. …… This is a story about a man who was mistaken for a Kryptonian with a template of the motherland, but is actually a sinister and black guy who is doing things in the world of superheroes.

- Description from novelbuddy