One Piece: Don't Worry, I'm a Doctor - Chapter 161: Help Me Save My Son!

While the demons were rising, mankind was about to become extinct. Six temples rose and protected the last territory of mankind.

Accidentally, she got pregnant.

King Grey has unrivaled strength, wealth, and prestige in a world governed by martial ability. However, solitude lingers closely behind those with great power. Beneath the glamorous exterior of a powerful king lurks the shell of man, devoid of purpose and will. 

Reincarnated into a new world filled with magic and monsters, the king has a second chance to relive his life. Correcting the mistakes of his past will not be his only challenge, however. Underneath the peace and prosperity of the new world is an undercurrent threatening to destroy everything he has worked for, questioning his role and reason for being born again. 

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.