Legendary Extraction: Kingdom Builder in a Ruined World - Chapter 8: Starting The Grind.

Ryoma Kogure, a high school student, is surprised when his childhood friend and best friend, Hirasawa Reo, who has always been popular yet indifferent to romance, suddenly confides in him about a love matter.However, when Ryouma learns that Reo’s crush is their quiet classmate, Otsuki Shizuku, he decides to help him out.While personally gathering information on Shizuku for his best friend, Ryoma is unexpectedly summoned by the school’s most beautiful girl, Asahina Alisa!She, being Shizuku’s best friend, mistakenly believes that Ryouma has feelings for Shizuku…!?Caught in Alisa’s misunderstanding, Ryoma scrambles to sort things out…As they began supporting their best friends for their own reason, Ryoma and Alisa grow closer——A romantic comedy that starts with friends supporting each other’s love!

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.

He rose from abjection and achieved eternity in glory.
He embraced the prettiest beauties and killed the strongest opponents.
He was able to shift the clouds into rain and cover the sky with one hand.
He could overrun the entire world and go anywhere as he pleased.
He pacified wars and held the world in awe.
He was matchless in the world.
However, his hair turned white overnight for his beloved woman and he was on the verge of death.
He was surrounded by enemies who were trying to take his life.
He struggled his way to become mighty and fought for everything he cherished.
For this age, he was the only king of the Dark World.
His name was a byword for might.
As a man living in the world, his only ideal was to pursue brilliance.

- Description from Novelupdates

[He is the villain in the house fighting essay, the roadblock in the spoiled essay, and the negative teaching material in the imperial examination essay]
His father joined the army and was named a marquis, but Mrs. Hou is not his mother, what should I do?
The stepmother seems to be transmigrating, gentle and virtuous, but in fact she wants to nurture him, what should I do?
The grandmother is snobby and wants him to give up the position of the eldest son. What should I do?
When preparing for the imperial examination, the relatives make trouble and want him to fail the examination. What should I do?
——The above answers are all in the “Complete Explanation of the Reverse Textbooks of the Imperial Examination”. This book covers family disputes, difficulties in the imperial examination, troubles in the officialdom, and the rules of power and ministers. I have a book in hand, I have the scientific test, and the teaching will not give a full refund!

Later, when the Xungui family taught their children to study, they would always take Xiao Jingduo as an example: “Study well, don’t go astray. Don’t imitate him, you won’t disgrace the words of the sages.”
* * * * *
People in the world have mixed evaluations of Xiao Jingduo, and what he is most criticized for is that he has no literati spirit, and is willing to be the sword of the regent princess and work for the princess.
Until later, Xiao Jingduo married the princess regent.
Courtier: …………No wonder!

This article is also known as “The Revenge of the Original Spouse”

- Description from novelbuddy