My Shadow Monarch's System - Chapter 19: Letter of Truce.

Lyle Walt is a young noble boy and heir looking forward to the day he can inherit his family’s territory. Except around when he was 10 year old, his parents started neglecting him more and more in favour of his little sister, Celes.
On his fifteenth birthday, he is challenged to a duel by his sister to see who will inherit the household and horribly loses, being cast out of his family. Afterwards, he gets treated by the family groundskeepers and receives the family heirloom Gem from him that Lyle’s grandfather had entrusted to him. From there, he begins an aimless journey with his childhood friend and former fiancée, Novem, and the Gem-turned-Jewel that houses the memories, personalities, and Skills of seven of his ancestors.

I traverse along the pathway of darkness and imagination…

As a good-looking Beta with a good family background, Duan Jiayan has lived a smooth sailing life for more than ten years, until he met Lu XingCi in high school.

Lu XingCi’s family situation is better than his, he is taller than him and plays basketball better than him. Needless to say, his grades are a whole tier above Duan JiaYan’s. Even his friends can’t help but occasionally praise Lu XingCi.

Most importantly, every girl that Duan JiaYan has set his sights on, all admitted that they have liked Lu XingCi for a few years already.

Since then, Duan Jiayan has never thought well of Lu XingCi, till the day he received his new medical report. He is a late-blooming Omega, and because he became an Omega this late, it came with dire consequences. Now Alphas will feel the need to beat up other people whenever they come near Duan JiaYan. He himself is now allergic to every Alpha’s pheromone, except Lu XingCi’s.

*

One night during a self-study session, Duan Jiayan became extremely uncomfortable and ended up asking Lu XingCi to bite him and leave a temporary mark.

After finishing the bite, Lu Xing asked: “We Alphas have very bad tempers, now that I’ve bitten you, are there any rewards?”

“Why don’t you…” Duan Jiayan tentatively asked: “Be a little more generous?”

“Sure,” the other party kneeled slightly and tilted down his head, exposing his white neck: “Then you’ve to also bite back. Once you do, I won’t make a fuss anymore.”

Duan Jiayan: “…”

- Description from Novelupdates

Having been reborn, she takes one glance at her ridiculously handsome husband and wonders if she had suffered from brain damage back then—she had actually demanded for a divorce with him. Repeatedly!