Building The Ultimate Fantasy - Chapter 613 - . I, Lu Pingan, will take it from here

“Future Occupation…Demon King.”

Sai Akuto enters Constant Magic Academy to be useful to society and to become a top-ranked national magician. However, a horrible prediction is made on his first day. Thanks to this prediction, the class representative girl hates him, a girl with a mysterious power embraces him, a female artificial human is sent by the empire to observe him, and his school life is otherwise thrown into chaos…

—She is a girl with a bright smile on the battlefield.

With her silver hair fluttering in the air and dark eyes, the girl sprinted on the battlefield. Her name is Olivia, whose hands is stained with the blood of her enemies as she shows an innocent smile.

The deep knowledge and combat techniques of the entity who called itself a Death God has been branded onto her body. On Olivia’s 15th birthday, the Death God suddenly disappeared. Olivia enlisted with the Royal Army and started fighting in the war as she searched for clues.

Lunar Calendar Year 998. The Kingdom has suffered consecutive losses to the Empire aiming to conquer the entire continent. The innocent girl who lacked common sense will step into the battlefield as the “Strongest Chess Piece” of the Kingdom, and go down the path of a hero—!

This novel is also known as Master Fu's Mysterious Darling Wife

She is the The Young Miss of Military family Shen, her face is peerless, her temperament is cold, and she is her family’s treasure, but isn’t accepted as one’s child by her mother;

He is The Sole Heir to the top giant Fu Family, his power is unparalleled, indifferent high-born, the captain of the mysterious military force, and the youngest commander-in-chief.

Because of her grandmother’s wishes, she married him at lightning speed. She thought that it was a marriage that she needed, but she didn’t expect to be greeted with his extreme pampering.

- Description from Novelupdates