The Heroine is My Stepsister, and I'm her Final Boss - Chapter 3: The Relentless Ego

In the 21st century Earth gave Birth to greatest genius ever. A genius who Master myriad of arts. Medicine to Engineering. Mathematics to Micro Biology. Weapon Designing to Environmental control. Music to Painting. Dance to Martial arts. He mastered Everything.

Having lived a normal life all his life and died without being able to fulfill his desire and when he’s given a task by a god, watch how he takes the protagonists girls while making it hard for the hero.

She shouldn’t have got drunk, so she wouldn’t have court the troubles.
She slept with a handsome man and would be sent to the police?
Oh, my sweet Jesus…
“So you just ran away like nothing happened after you slept with me?”
“Old jerk! Even if I had the initiative, it was you who took advantage of me!”
As a saying goes, the more spoiled a president gets, the more likely he becomes a scumbag.
An adorable ‘wildcat’ vs. a scheming frenemy.
This was a love rivalry between a modern Cinderella and a Big Boss.
As time flew, the world was like a fleeting show.
When they met again after several years of separation, he held her hand tightly and swore that he would never give her any chance to leave him again!
Finally, he asked her to marry him and pampered his cute wifey with his endless love.

- Description from Novelupdates

The powerful have caused chaos for all that are lesser than them since the beginning of existence.This is the story about the truth that everyone knows but no one realizes.The story of a king who failed his duty, a dragon who lost what it held most dear, a beautiful girl who lost who she was and a fae that was once a queen.Cades Kirgun is an ehetrian child, one that longs to become an artificer.But his plans go awry as his whole world collapses and he needs to flee.How will he survive ?How will he overcome the challenges presented to him and overthrow those that have held the power for far too long ?This is the story of a king born from rags, a king that leads to people to fight for what they believe in, the crusader king.