MTL - Time is slow - Chapter 563 Marriage is settled

A scientific genius named Thomas Harrier was transmigrated to an imperial prince body after a car accident that took his life. He found out that he is in a world similar to our own with a timeline akin to early twentieth century. The body that he is occupying was the imperial prince of a failing empire who suddenly rose to power after a successful assassination attempt of his father. Unaware that the attack is just the beginning of what is to come. He faces many challenges throughout. Will Thomas Harrier be able to live his second life in peace while running an empire and getting it back to its former glory? Or will he succumb into a conspiracy lurking within the country's borders?

Expect some:

Cold war era techs.

Super battleship with advanced electronics, propulsion, and fire control systems?
Helicopters?
Missiles?
Modern medicines and equipment?
AC-130?
A nuke?
Challenger or Abrams or Leopard?
F-4 Phantom or MIG-21?
Colored TV's.

Everything!!!

PS. Cover not mine, I just found it on google.

He swore that if he was given a second chance to live, he would live his life to the fullest.His life was full of misery but he was reincarnated in the body of the son of the strongest expert in the empire.He had the looks, wealth, and women. He was known as the “Handsome Playboy” and he didn't want to become a righteous protagonist.He awakened a system that can make him strong by making others feel the 7 sins towards him.He will collect many beauties and live to the peak of life.

A class full of idols and beautiful people are sent to another world. However there is one guy who is ugly, fat and smells… our protagonist. This is his comedic story of evolution and the slow building of his harem. The first heroine is a gorilla.

By the year 3029 CE, Earth’s technology has developed rapidly, borders no longer exist, and Earth has been unified, marking the beginning of the era of the Federation.

At that time, a huge sword flew from the heavens, piercing the sun and causing a huge sensation on Earth.

Perhaps because the scabbard of the sword was already in tatters, countless shards have broken off from it following the collision with the sun and spread across the universe. Many of these shards have landed on various places across Earth.

With the arrival of the bronze sword and its shards, a new unlimited energy source has suddenly appeared on Earth. This energy source has since been named Spirit Qi.

Spirit Qi is like air, thick in some places and thin in others. As the Federation and other factions gather more shards, they discover more information on cultivation, pill refinement, Spirit Stone refinement, and other techniques. The words on the shards have an ancient feel to them, making it a trend for people to use ancient language.

The appearance of Spirit Qi rapidly makes the original energy sources obsolete and has completely changed people’s lives. Not only has the Spirit Internet been formed, Spirit Qi has also changed the course of Human Civilization, causing the world to enter a civilization of cultivation. This would later come to be known as the Spirit Inception Era.

- Description from Novelupdates