The S-Rank's Son has a Secret System - Chapter 19: Surface Tension

[You have entered the dungeon at Gwachun Station’s 1st Exit.] When former high school student Kang Woojin finds himself returned back to Earth after being forcibly summoned to a foreign planet for 20 years, he soon finds that Earth is not the same, normal place as he once remembered it to be.

She was once an heiress, but later her family went bankrupt, and her fiancé betrayed her. Besides, she had to bear the expensive medical expenses of her brother. Therefore, to regain everything, she decidedly married her ex's cousin in a deal. Initially, he was very aloof and didn't care about women at all, but he gradually fell in love with her, protecting her and supporting her...

In the tenth year after the new era, the world finally came to an end. Zhang Mu truefully waited for his death, but unexpectedly found that he had returned to ten years ago. With his memory about the future, he swore that he would change the calamitous history, saving the earth from being destroyed! Walking dead, zergs, evolvers, and various mutated animals… nothing can stop him! The first step is to retrieve his identity as an era merchant , then find all the treasures he can remember to enhance himself!

- Description from Novelupdates

Rei just wanted to read novels in peace, no girlfriends, no drama, no accidental death by divine lightning meant for a cockroach…But for now, he is the son of a powerful duke, reincarnated into a fantasy world full of magic, monsters—and dangerously obsessed women.They were childhood friends of that duke son. They all are sweet noble girls. One is emperor’s daughter and one is my older sister. Now they’re grown up… and they all want one thing.And that thing is Rei.Welcome to a world where love means stalking, loyalty means stabbing your rivals, and marriage proposals come with blood pacts and fireballs and even my system mocks me. Rei fiancées battle each other daily and his life is a romantic comedy… except it’s also a warzone.Oh, and his final mission is marry the Demon Queen. A literal succubus overlord trying to conquer the world.Somebody please help him. In a realm of swords, sorcery, and yandere chaos. So, he can find peace or at least keep his limbs attached.