Harem of the Demon: Gathering Beauties in a Magic World - Chapter 29 - . The Apprentice Also Wants in on the Fun**

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.

On the will left behind by the 14 year old suicide victim K:

“Taku Sugawara is the devil. Nobody should believe his words.”

After spending half a year in the province, Cheng Yang took a luxurious cruise for seven days.
Accidentally hooked up with a CEO on the way.

Later, Cheng Yang found out that he was pregnant.
Just as Cheng Yang was preparing to secretly give birth to the baby, it was a coincidence that he fell asleep in the big president’s bed.

It’s impossible to run with the ball, his man is handsome and rich.
Must cling tightly and can’t be torn down.

- Description from Novelupdates