MTL - Global Killing: Awakening SSS-level Talent at the Beginning - Chapter 1122

Once I’ve become Immortal, then my attempt to conquer the world shall begin.

In the ancient land of Yamato, seven powerful clans rule, each upholding their own traditions and strength. But when one clan seeks forbidden power, the balance of the world is shattered. Legends tell of warriors destined to rise, of a hero who will walk the sacred path, and of a battle that will shape the future of Yamato. As alliances are tested and enemies emerge from the shadows, the line between justice and power begins to blur. Will strength alone decide the fate of Yamato, or will a greater force change its destiny forever?

However, he did not know that he was not raising just a harmless pet, but a biological weapon secretly made by the government… a real monster.

As a former librarian, Rand felt that he had been living an ordinary life, the one that he had reclaimed unconsciously every single day.

Recently, he has been a little upset because the pet fish he accidently brought home to raised seems to have undergo some strange changes

Well, it turned into a merman.

- 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