The King of Beast Trainers - Chapter 205 - 130 No Way At All_2

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

I opened my eyes to find myself in another world. For some odd reason, I ended up as a sword. Before my eyes laid a plain full of magic beasts, and so, I launched my body and flew in search of a partner, a wielder (females only).

This story revolves around a boy who was sent to a dark, mysterious parallel world in the body of his beautiful senior sister known as Lily. The lone girl ran into the night parade of a hundred ghosts the very day she arrived; seeking survival amongst the warrior’s dispute in a chaotic world, and forging her own demon sword! This is an unimaginable other world adventure!

She was originally the king of the dark mercenary world, killing, plundering, and looking down on the world; once reborn, she became a powerful family that shocked the continent, the “Ninth Young Master of Waste” of the Beiting family;

From then on, the elegance of the world, shake hands;

Belonging to ancient monsters, possessing a magical space, practicing heaven-defying skills, killing the sky, killing the gods, and doing whatever they want;

Cool and handsome, domineering and arrogant, leading the world to compete;

In this article, the male and female protagonists are double C, male strong + female strong, and the ending is one-on-one;

- Description from novelbuddy