She's a Passerby, But Can See the Protagonist's Halo - Chapter 90

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

Gu Mingxi and Pang Qian were next-door neighbors, classmates, and deskmates. From year-to-year, even when the class seating was rearranged, they would still be deskmates. They grew up together like a pair of brother and sisters despite having different parents; if it was someone else, then their parents would probably have already arranged their wedding. However, Gu Mingxi was different.