Geometric Mage: First Spell, Circle - Chapter 28: Stronger

Song Yu, an up and coming architect was supposed to be the fiancée to the second son of the Qi Family… until her family went bankrupt. The engagement was called off and she finally has the freedom to love whoever she wants to! Years later, a twist of fate made her cross paths with the Qi family again. In order to land a prestigious architect role in an upcoming hotel construction project, she had to impress the director of Qilin. Follow Song Yu as she navigates through life and love!

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

After dying, you wake up and realize you've been reincarnated as a background character who is judged as human trash.The decision to change your destiny comes instantly.Discovering that your identity isn't as simple as you thought, you feel favored by the heavens when you manage to become a powerful character.Katase: You won't fool me. I'll expose you for the pervert you are.Murayama: ...Thank you for saving us.Issei: Motohama, what happened to you? How are you so powerful?Rias: If you join my peerage, I wouldn't mind being yours.Sona: You beat me in the game. That means you're now my fiancé.Yasaka: Honey, Kuno wants a little brother.Kaori Houjou: Shinji-kun, let's go on an adventure.Kaede Kazama: Shinji-kun, thank you for saving me from that ball.Rie Sawada: Shinji-kun, I'll wait for you. You'll be my future husband, fufufufu...Changing known history and taking it in a direction not even his eyes could perceive, he didn't stop no matter what. Not even the other world was safe from his clutches.Lexia Von Arselia: My hero, and my future husband...Shinji advances without stopping.“I, Shinji Motohama, swear here and now that I will reach the top of both worlds.”

Originally, the question Tang Xian was thinking about was whether he should be a hero for a second among this group of destructive bosses, or continue to pretend to be a boss.

Later he found out that if you pretend to be fake, it becomes real.

- Description from novelbuddy