Became a Medieval Fantasy Wizard - Chapter 13:

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

Nagi who was summoned to another world acquired the「Skill Structure」skill.

Nagi felt the hints of black job from the king’s request 「To defeat the devil king」. He leaves the castle and starts his journey with a slave girl.

The small demon girl Cecyl, the melee-fighter beast girl Rita , Aine the onee-chan maid, Regii the cursed sword.

Rafiria the warm and fluffy elf and Iris the sea dragon shrine maiden.

Nagi rewrites the girls’ skills and made them into 「cheat characters」one after another.

The world is full of mysteries. Strange, seemingly unexplainable events occur more often than we may realize. A young boy may catch an illness no doctor can explain. An office may catch fire for no apparent reason. And perhaps, someone may die a sudden and unexpected death – their bodies blighted beyond recognition.

“Compared to our time, the current generation just aren’t as reliable” they said, “Still, isn’t he the son of the Hero?” How annoying.

It’s been over ten years since the battle between mankind and the demons ended. The children of the heroes who saved the world are all grown up.

One of them, Earth, was a talented man, and everyone expected him to succeed his father as a warrior and defend his country, but Earth was always wary of his father’s title.

One day, Earth is shocked to find his father’s sword, which was used to overthrow the Demon King, sealed in his family’s mansion.

Because trapped within was the ghost of the Great Demon King who was unable to pass on and continued to roam the world.

For some reason, only he could see the spirit of the Demon King, and the Demon King possessed him through the sword.

Every day, forced to coexist with the spirit of the Demon King, they live a strange shared life, when the Demon King whispers to Earth on a whim.

“I have a grudge against your father. If you want to get back at your father and the world, I’ll train you. I’m free.”

Earth receives special personal guidance from the Demon King just to get back at his parents and the world.

Then, in the coming days. The hero’s parents, the heroes of the past, the first love, the princess childhood friend, the geniuses of the era, and the world will tremble.