Ghost Billionaire - Chapter 38: One of Them

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.

[R18 novel with a lot of sexual content]Artem never expected to take on the role of a villain, let alone transmigrate between harem novels. Bound by a system, his task is clear: steal the heroines from all the protagonists’. From Chinese Cultivation and Korean Gate to Japanese Isekai Fantasy, VRMMORPG, and beyond—no heroine is off-limits, and no protagonist is safe!

“My name is Shun Satsujin. I'm an orphan… and someone who died only to be reborn into a world filled with fictional stories I once knew.”I expected a cheat ability—something powerful or overpowered. But all I got… was an intense exercise method called Herculess Method and a challenging life.Now, I'm just trying to survive and stay on track.That was the plan—until I enrolled in Shuchiin Academy.And suddenly, I found myself surrounded by girls from anime I used to watch.One by one, they started getting involved with me.

I was reincarnated into another world, and I’ve brought the Horadric Cube from Diablo II with me.
Being a knight is cool and all, but being a wizard is pretty neat as well.
So, which one will it be?

- Description from Novelupdates