MTL - The Rebirth of the Malicious Empress of Military Lineage - Chapter 142 Alliance

When Xiao Fei was three years old, he was caught by a man with a sharp-nosed monkey and taught him to cultivate. The old man is Sun Wukong. In the past ten years, he has taught him the eyes of the fire, the copper and the iron bones, and the great product of the immortality… After the learning, Xiao Fei went down the mountain and accidentally entered a noble school. Pure school flowers, the best Lori, Miss Qianjin, beautiful maid… I like to sleep with him. Oh no, it’s a friend.

- Description from Biquge.com.cn (translated)

In an era when the power of Fire Magic was considered to have reached its limit, one girl began researching nuclear fusion.

Because her appearance was not breathtaking, the Emperor breaks off their engagement and bestows her instead to the bloodthirsty, ruthless, and cold-blooded Second Prince (Wang Ye).

On her wedding night comes endless humiliation, the genuine Princess Consort becoming a deserted women. A foolish woman before rebirth, she no longer expects his love. In this world, she must possess enough talent to awe those around her, carrying herself with composure and articulating with beautiful diction, override above the nine night.

- Description from Novelupdates

agreed. He thought they might just talk, have a few drinks, and that nothing significant would happen. However, she invited him to a hotel, and they spent the night together.The next morning, she told him it was just a one-night stand and that they would probably never meet again. She said goodbye and left. Ronan also decided to treat it like that.The next day, at his college's hosting club, Ronan was given the responsibility of hosting that year's annual function, where they had invited a singer.When Ronan looked up at the singer, he was shocked—it was the same woman he had spent the night with. After checking her history and social media, he formed an impression of her. Every picture she posted was in revealing clothes, bikinis, or almost nude outfits.He concluded that she was just a promiscuous woman, likely driven by lust, and that she had probably chosen to spend the night with him simply because she found him handsome.Understanding this, Ronan decided to focus on his work. That morning, she had made it clear that it was just a one-night stand and nothing more. He would treat it exactly that way and carry out his responsibilities.Protagonist has System---No NTRIt's Harem, with many girls but The Singer is Main Heroine.