HxH : Pokemon Master - Chapter 87: The Strongest Floor Master of the Heaven’s Arena!

Mu Zhiyan, after being transmigrated a millennium (1000 yrs) into the future, discovered that he was raised by his adoptive parents as a tool for them to access the heritage his (dead) biological parents left behind. When he was at a loss for what to do next, he discovered that his body hosted an additional
pharmaceutical system.

For a chance to return to his era of Earth, Mu Zhiyan decided to practice and practice; he must train the system to full level as soon as possible.

However, reality gave him a slap in the face. The world is dangerous and dreadful, making Mu Zhiyan recall his mother’s words of holding a thick thigh, resulting in him locking his eyes on a cool general…

So the rumored mysterious Mu Master faced General Han with a serious face: “I allow you to follow me, General Han.”

General Han: “…”

- Description from Novelupdates

A biker tries to save a cat on the highway and gets hit by a truck (Truck-Kun), he was rushed to the hospital but, due to internal bleeding, he dies only to be reborn as a cat, in a new world with a system.

In this new and vast world, he tries his best to get used to his new body and get stronger along the way. With his overpowered system and skills. To one day become untouchable.

A world where the [Demon King] was defeated by a [Hero] that came from another world. People carelessly forgot about their fear of the [Demon King] and of monsters, living in peace.

In a forgotten and run-down cave in the mountains, a new monster that should not have been born was given birth.

The monster’s name was the [Black Ooze]. It was nothing exceptional other than its black color, an ordinary slime.

However, this slime had the special characteristic of being able to take the abilities of the living things it swallowed. It preyed on an insect that had paralytic poison, as well as other animals. Following that, it attacked a human, obtaining his knowledge and [Desire].

Before long, the monster established its target as the female mage that came to explore the cave.

This world still wasn’t aware.

A slime randomly falls into existence. Sapient and born with the ability to recreate parts of the things it preys upon, the highly confused drop of primordial soup decides that the only real thing it can do is become the being at the top of the food chain. A task of longevity in the leaves of the Omniverse.