Isaac - Chapter 187

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

After her mother’s passing, Tabitha Collins’s father marries a new wife and sends Tabitha Collins to live with a family she barely knows. There, she meets Alexander Foster, the family’s high-flying Eldest Young Master, who wants nothing to do with her. Apart from him, however, the other members of the family loves her and dotes on her. Soon, things began to change. Alexander Foster becomes intrigued by the mysterious and seemingly untamable Tabitha Collins. Who is she exactly? Initially, the girl seems to lack confidence and needs protecting, but as he finds out more about her, he realizes, he's the one with the catching up to do!

A hundred years ago, he was a genius of the Emperor's Domain who made even the God of War wary. He was unparalleled in both alchemy and martial arts. However, his friend betrayed him, leading to his untimely demise.A hundred years later, he rose from being a dandy young master, starting everything anew. From then on, the world witnessed the emergence of an extraordinary genius.“Boss is even more ferocious than a wild beast!”“Boss values friendship above all else. He is forever my best friend!”“Kevin, no matter how long it takes, I'll wait for you. I won't marry anyone else!”“Don't ever provoke that man of calamity. That guy is a beast!”“I am Kevin Anderson, who dares to defy me?!”

This world has Fox Fairies, River Gods, Water Monsters, Great Demons and Cultivators who seek immortality.