One Piece: Fist of the World - Chapter 63: The Second Devil Fruit

A master assassin transmigrates into an interstellar era.

Chu Feng was transmigrated to a world of tamers, where everyone would gain their unique tamer talent at the age of 16. With the tamer talent, one could create a tamer space and form a contract with a beast.

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

The teenager Long Ao, ten years of silence, was reduced from genius to waste, and was ridiculed and mocked.

Ten years of persistence, ten thousand failures, and finally won mysterious Dragon Seal.

With Primal Chaos Saint Body, cultivation invincible cultivation technique, refining Heaven and Earth, devouring endless stars, sweeping the wasteland! Ask the vast stars, who dares to fight me? Boundless Starry Sky, War God! …

- Description from Uukanshu