Hidden Assassin - Chapter 44

The Empress who dies in torture, An Rushuang is her name. After she wakes up, she finds herself has time-travelled to when she was twelve years old, but she would turn into Major General’s white horse at night. He is a general who orders about the winds and clouds on the battlefield, and she is a little girl lives in her boudoir seclusively.
She endeavors to change her fate, and he spared no effort to win every battle. They meet each other every day, well, it’s night to be accurate. Is that a dream or not? She pleads to marry the seignior to win peace for her family, only to find he is the one she is going to marry.
“Growing old with you under the same roof is my long-cherished wish”, thought them both.

- Description from Novelupdates

This legend tells the tale of the protagonist, Kuroki summoned to protect the demon king from the hero.

Kuroki, unbeknownst to him, suddenly came to another world. He was summoned by the demon king, Modes. The territory which the demon king overrules was in the midst of being destroyed because of the hero. He had no choice but to bow before Kuroki.

“Please save us, Savior Dono!”

Kuroki nodded, deciding to save the demon king due to an unexpected turn of event.

18 and naive, Belle Hart thought marriage would end her misery, only to realize it had just begun!What started as a promising love turned out to be a facade, would Belle choose between a second chance or leave? She met her mate, the Duke, who she proposed to when she came of age.A month in, things took a turn. The Duke leaves for war before she could inform him about her pregnancy, only for him to return with a mysterious woman whom he claimed to be his new wife! The audacity! Trouble ensued and Belle suffered a miscarriage as a result.…“What did you just say?” He asked, his gaze darkening.“You heard me well, I seek a divorce. I wish for us to go our separate ways,” she replied, her voice steady as she met his gaze with confidence, though inwardly she was shaken by his presence.“You are my mate, Belle, and I am yours. Divorce is the most foolish notion you could entertain. Do you believe any man would take a worthless creature like you as his wife?” He scoffed, his words biting, causing her heart to ache.…The Duke's refusal pushed Belle into the arms of the king. All she had to do was bear him an heir and he would help her get her revenge!“I want you to marry me, Your Majesty, and aid me in seeking my revenge against the Duke and those who have wronged me. In exchange, I shall bear you an heir before you help me,” she said, her voice steady and full of purpose.What will the choice be?

The dawn era after the end of the half century has gradually rebuilt the order, abandoned civilization, and is full of undivided violence and desire.
The noble and powerful pioneers are in charge of the city, and the evil and mad plagues are in the wilderness.
Pure human beings who cannot mutate are the weakest, dominated by the rulers of the pioneers, and are not as good as animals in the wilderness.
A purely humanized young man with a worldly experience has quietly entered the WTO, holding a three-foot long knife and a long-distance desire to boil in the world of purgatory. From the nameless name to the sorrow of the Supreme Court, the name of the black ride is resounding!

- Description from Uukanshu (translated)