MTL - The Fallen Merman - Chapter 149

Zheng Tan somehow returns to the year 2003, turning into a black cat. Picked up from a rubbish heap by the Jiao family, he is given the name “Charcoal”, and so begins the life inside Professor Jiao’s family. Zheng Tan remembers that he was once a person, but currently his body is that of a cat. He has no way of speaking the human language, but can understand it, and even retains the thinking and IQ of a young 20 year old youth. Read along as he adapts to this new world, and somehow tumbles from a group brawl to catching a thief.

- Description from Novelupdates

I lived my whole life as a s*ave, bound by a leash. But there was one thing that I was able to choose for myself: the place where I would die.“…Any last words?”My only friend asked me in a calm voice, and I quietly replied as I closed my eyes.“Waaaah!”…Waaaah?To cut to the chase, I was reincarnated. And not just as anyone, but as my friend’s youngest grandson. So, what am I going to do now? Well, what else can I do?“I’m going to cause chaos.”

The simulation is over, and the entry is obtained: a showdown!

Looking at this entry, Zhao Meng was stunned.

“How should this term be used?”

“Hey! Here’s a wounded fox!”

…

A few years later, a woman who looked like a fairy appeared in front of him, and said:

“My lord, I’m here to repay my favor!”

This book is also called “Starting from Transforming Monsters”

- Description from novelbuddy

“Young man… if you could go back in time, what period would you like to be in?”