As Sukuna in Invincible - Chapter 74: Okay... Chill.

The Realm of Omnidom have five planes of reality, and nobody ascends them alone. You rise with your kingdom — through wars, through victories, through every moment that should have finished you but you overcome it and broke through to see the next wonders, win the next conquest, and kill your next foes.Everyone who arrives gets the same deal. A universal system, a voice, a blank patch of nothing and the nerve to call it a kingdom someday.See, people built some wild things here. Abyssal Underwater Civilizations. Cloud empires. Cities inside trees so massive they have their own weather systems. Floating eldritch continents that only seek conquests and horrors. And much more.Genuinely breathtaking stuff.But mine tops them all.The ones that came before me are history. The ones that came after me are comparisons. And the ones that tried to surpass me?Good stories. Tragic endings.Want to see how that happened? Then get onboard. It's a wild ride.#Kingdom Building. #Strong/OP Growth MC. #No-Harem. #Progression Fantasy. #Summons.------[ Discord: https://discord.gg/MSM9Gp3Jxz ]

He died on the wedding of the girl he had a crush on, after a long and successful career. After convincing Yama to send him back to the world, he decides to fix the areas in which his life went wrong. Realizing the lack of love and romance in his past life, he sets out to conquer the hearts of various women.

For the large sum of money to help her husband, she chose to be a surrogate mother covertly. Her sweetheart was out of trouble, but she became the woman of loose morals in his eyes. Misunderstanding, disappointment and sadness forced her to divorce the man she loved from the childhood.

When she was determined to start new life, another man burst into her life. “You are my baby’s mommy and you are my wife!” A big surprise hit her that her baby’s Daddy, the man she surrogated for, fell in love with her at his first sight.

His deep love convinced her to believe the affection of love again. Unexpectedly, her ex-husband returned to beg her recombination. One was her childhood sweetheart, and the other was the man who loved her and gave her hope for a new life……Facing the two men, what is her choice?
 

- Description from Novelupdates

Another entry in what you can call the Proto Harem Series: the books written before the Harem Series that take place in the same world.

It’s about a swordswoman whose student is captured, so she goes to rescue her.