MTL - The Rise of Dark Pokemons - Chapter 252 Can't afford

Yuki, a high school junior, dies heroically saving a stranger and is reincarnated in a fantasy world, where he discovers an extraordinary and unrivaled power.

A generation’s War God, once overlooking the world with disdain, had fallen into disgrace because of a conspiracy, becoming a mere son-in-law. However, what nobody had expected was that it was all part of his grand scheme, and when the winds of change blew, he, the king, returned, with the power to overturn seas and move mountains, as a dragon ascended to the heavens!

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 a world teeming with Titans, Colossals, Gigantic Monsters and Kaiju's, Erian who reincarnated makes his living collecting scraps of low-grade Defective Genetic Serum, realised he transmigrated along with his system.

Follow Erian as he grows to become the strongest Disaster Grade Titan with the help of his Titan System!