Kyoukai Senjou no Horizon - Volume 2, School Rules

Amidst a world plunged into chaos, where rituals have collapsed and music has spoiled, and the universe is muddled, Gu Qingfeng finds himself transported to this tumultuous era.Initially, he only desired to live out his remaining years in peace. However, the birth of his first son made him realize that things were not as simple as he had imagined...

Enemies always meet on a narrow road and when they meet war breaks out.

They met as kids and fought but Zi Han lost.

They met in the army as recruits and even then Zi Han lost.

He lost again as he remained a sergeant while Yi Chen was promoted to the position of Marshal.

Even when his dark history swallowed him whole and shifted allegiance to become the Universe’s most infamous assassin he still lost to Yi Chen.

Zi Han, “Damn it! Why won’t you let me win.”

Yi Chen, “I can let you win in bed if you like?”

Zi Han, “……”

When did enemies graduate from rolling in the dirt fighting to rolling in the sheets….. fighting? That’s the million-dollar question.

.....

Xue Xi is forced to fall in love at first sight with this dangerous man on their first meeting. With death being the only other option, she makes the first move:

One night she gets drunk and mistakes the most well-known Mafia boss for a host and intends to sleep with him.

Oh my! What should I do? It’s best to run away!

- Description from Novelupdates