The Spider Queen - Chapter 45: Invitation

A supreme expert in the Immortal World had died, and a strand of his soul returned to its original body on Earth. Tang Xiu discovered with amazement that ten thousand years passed in the Immortal World, yet only a single year passed on Earth.

Ruthlessly betrayed by his lover and trusted friends, Tang Xiu found that his soul went back to his previous body on Earth, and, despite he spent 10,000 years in the Immortal World, just a year has passed on Earth and many things have changed. Having an unsurpassed knowledge, Tang Xiu will protect his loved ones and go back to the Immortal World to take his revenge.

- Description from Novelupdates

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

“They say the eyes are the window to the soul.”But what if your soul isn't human?Yuki always felt different... too quiet, too distant, too aware of things that shouldn’t exist. But when a strange voice calls him kitsune under a moonlit sky, his world shatters.Awakening powers he can’t control, chased by shadows from a forgotten world, Yuki is thrown into a realm of spirits, mythic creatures, and ancient war.As his true nature begins to surface, so do enemies... and allies... with secrets of their own.This is the beginning of his awakening.And the mythos has only just begun.

The boy who Sneaks in My Bedroom Window