Tunnel Rat - Day 1: Nothing Changes, Everything Changes

Witnessing her boyfriend cheating on her with her bestie, Shiyao was so angry that she went to a pub for fun and met a man, who was really a piece of work. After a crazy night she fled away, but was embarrassed to know that the man she slept with was her boss You Ze.
Jesus, give her a break!

- Description from Novelupdates

A hundred years ago, he was a genius of the Emperor's Domain who made even the God of War wary. He was unparalleled in both alchemy and martial arts. However, his friend betrayed him, leading to his untimely demise.A hundred years later, he rose from being a dandy young master, starting everything anew. From then on, the world witnessed the emergence of an extraordinary genius.“Boss is even more ferocious than a wild beast!”“Boss values friendship above all else. He is forever my best friend!”“Kevin, no matter how long it takes, I'll wait for you. I won't marry anyone else!”“Don't ever provoke that man of calamity. That guy is a beast!”“I am Kevin Anderson, who dares to defy me?!”

By the fourth year of Su Wan's career, every league rookie hears the same warning from their coach and veteran teammates: “You can try to impress him. You can even try to defend him. But no matter what—no matter if he hurls the most brutal insults your way—never, ever talk shit to him!”

The maniac who was crazy about all kinds of fields such as military and steampunk had been reincarnated.

However, his father was King Sejong the Great?

The mania-wise king and his crazy maniac son.

Along with the ministers, and countless humans who were getting exploited.

Even today, the night of Joseon was filled with the light of overtime.