Reborn as the Princess' Knight (GL) - Chapter 220 78:

Hou Niao, devoted to seeking the Dao, found himself mistakenly sent as an undercover agent to the Demon Sword Sect, eagerly anticipating the day he’d be rewarded for his service and could return to the Daoist Sect… Only when he had become a towering figure in the Sword Dao did he sorrowfully realize that there was no one left with the power to recall him!

Every drop of this family bloodline is stained with sin. They are the embodiment of contradiction; calm yet maniacal, with great memories yet often forgetful. They pledge themselves to their dreams yet often compromise, are angels that are also devils… It’s why I hate them. And also love them.

The only hope of his family, a youth with the blood of elves and devils walks on a battleground of annihilation and rebirth. He wills his way through boiling lava and icy depths, killing on this field of despair to strike down the lofty figure in his sight. One day he’ll grasp his blade tightly and survey his surroundings, only to find no more enemies to kill.

When he opened his eyes he found that he had been reborn as an extra in a novel, which he finished reading yesterday. On top of that, he has become a student of the same battle academy, where the main plot will happen. Let's accompany Rio on his journey and find out where it leads us.“i will steal protagonists chances, as for what will happen to main plot if i do so? i don't care!” (Rio)*The book cover doesn't belongs to me if someone wants me to take it down please contact me directly.*(MC is selfish and cares most about himself, rather than following the main story he will follow his own will. and there's no harem too.so, if you like a hero of justice and a plot following type mc with a harem or something then this is not your cup of tea.)

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