One Piece: King of the World - Chapter 140 - : Sengoku: Saint Claudius is My Patron!

Long Fei, a cross-timer and doujin, is an otaku who traveled to another world. In the original world, he was an otaku fan of Gundam and military science fiction.

He died in an accident and was reincarnated into another world. The Gundam works he had read before his death and the techniques in various military novels could be brought to another world.

How would he use the Gundam that Long Fei created? What waves can be caused in this different world?

- Description from novelbuddy

Humanity was living peacefully on Earth for millions and millions of years until the day unknown monsters from beyond space invaded them.

When humans were about to disappear, some people with abilities came out to the light and shared their knowledge and powers with the world, and together, they managed to push back the invaders during a terrible war that had lasted for years.

This war had created many orphans, and among them, Kye had lost everything, even his parents. And the only thing he received from their death was a pale-looking necklace.

However, once the necklace finally activated, a system was given to him, and his life changed completely.

The system gave him quests to do, and Kye complied. He was getting stronger every time he achieved them, until the day it gave him a weird quest.

[You have one day to kill the one who had sinned. If you do not kill, you will die.]

The previous lords have committed as many atrocities as possible to fill their bellies. I, the only daughter of that house, had discovered that my servant and lover was a spy.

And as the people wanted, my life ended with my execution.

However, with the memory of getting beheaded intact, I began a new life. I was planning to shoulder the sins of my past life and become a nun, but by some trick of fate, I came to work as a maid for the current lord.

Under my former lover, whose name, age and even hair colour were all lies.

Xiao Rou, a girl growing up in a poor countryside family, finds that she’s actually the daughter of a wealthy couple. Her mother had mistaken another girl for her back at the hospital. Thinking she would change from an ugly duckling to a noble swan and live happily ever after with her real family, reality strikes her in the face.

The other girl, Xiao Jinning, who had taken her family, her fiancé and everything else from her, uses every mean possible to frame her up, so when she returns to her biological parents, she finds her parents despising her while still doting on Xiao Jinning. Framed as a thief, she is expelled from the family and as soon as she walks out the door, she gets hit by a car and her spirit dies a miserable death thanks to Xiao Jinning.

Meanwhile, Tang Xi, a real princess, the heiress of the powerful Empire Group, is murdered by her greedy relatives. When she opens her eyes again, she finds herself in another girl’s body. She has become Xiao Rou and has a magic system—008 in her body! With the help of 008, she begins her journey for revenge. She would avenge poor Xiao Rou, punish her murderers, become the most famous star, and… make up with her true love—Qiao Liang.

- Description from Novelupdates