Turns Out, I'm In A Villain Clan! - Chapter 37: The Art of Shamelessness

An advertising director is reborn in 1988 Hollywood as an eighteen-year-old blond-haired westerner named Eric Williams.

Office worker Leon is reincarnated into a particularly punishing dating sim video game, where women reign supreme and only beautiful men have a seat at the table. But Leon has a secret weapon: he remembers everything from his past life, which includes a complete playthrough of the very game in which he is now trapped. Watch Leon spark a revolution to change this new world in order to fulfill his ultimate desire…of living a quiet, easy life in the countryside!

In novels with a stud there is always a Senior Martial Brother like this:

In the early stages of the novel, his innate talent is high, his cultivation is good, his appearance is handsome, and he has an intelligent, cute younger Martial Sister as a fiancée.

In the middle stages of the novel, he is caught unprepared and defeated by a young disciple (the protagonist) in the sect who’s hardly remarkable at all. From then on, he falls from his godly altar and loses his brilliance. Even his young Martial Sister leaves him for someone else.

In the late stages of the novel, he continues to turn dark, going down the Demonic Path and becoming the major villainous boss. However, the protagonist still ruthlessly defeats him and his soul is eternally sealed.

Once Qin Mo opened his eyes, he discovered that he had become this Senior Martial Brother.

- Description from Novelupdates

In a world dotted with World Entrances to a demon world, demons have invaded humans for centuries. Humanity has united and one of the most ancient sects in the world, the Archean Mountain Sect, has set up an entire education system in the form of Dao Academies and defenses at the World Entrances.