Reborn As A Nobody: Making A Harem - Chapter 1: Reincarnation

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)

He wants indoor plumbing. They think he’s conquering the world.Arthur was a genius engineer on Earth, capable of optimizing global logistics and automating entire factories. But he lacked one thing: common sense. Now, reincarnated as Arthur von Pendelton, the six-year-old son of a powerful Duke in a medieval fantasy world, he faces his greatest challenge yet: Drafts.Armed with the T.E.C.H. Interface (Trans-Epochal Construction Heuristic), Arthur can analyze magic like code and build modern technology from scratch. His goals are simple: Double-glazed windows, hot showers, and a toaster that doesn't burn the bread.But there is a problem. The people of this world don't understand engineering.He builds a high-pressure boiler for a bath; his father thinks it’s a “Dragon-Breath Siege Weapon.”He creates a hydroponic garden; the local church declares him the God of Harvest.He ignores a Princess's flirting to analyze the thread count of her dress; she thinks he is playing “hard to get.”Follow Arthur as he accidentally industrializes a kingdom, terrifies his enemies with home appliances, and remains completely oblivious to the fact that he is becoming the most powerful man in history.All he wanted was a warm bath.

He Tiantian had always treated the people around her with a grateful heart. Yet in her middle age, she discovered that she had been living in a deception filled with lies.Returning to the past, He Tiantian, with the assistance of the Little Silver Snake, began a new life.From a different perspective, so that was the truth!In this life, she would never again be willingly blind.In this life, she would never again miss out on or take for granted her childhood sweetheart, who had treated her with true affection. She would treat him well, trust him, and have a warm home.******

When he returned to the World of Martial Arts, the game was filled with blood and battles! Chen Kaixin had chased after the footsteps of the one emperor, two empresses, three princes, seven dukes, and thirteen aces for three years, but during the eve of the Sword Among Us tournament in Mount Hua, he was ambushed by evil bastards, and was killed so much that his level dropped to that of a newbie. He completely lost the chance to join the ranks of the powerful players in the game! In great disappointment, Kaixin quit the game and got drunk so that he could forget his sadness, but during that stormy night, Chen Kaixin found that he had actually dreamed for a total of three years, because when he woke up again, he woke up to three years ago, when he was still a student.

- Description from Novelupdates