Overlord (WN) - Volume 2 Chapter 18

An unknown parcel arrives to Yoshio, a 30-years old NEET. The content is a game disk titled “The Village of Fate.” A beautiful CG game with real-life images gets started.

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.

Ming Luo is a wasted daughter of the Duke Yi’s household. Her father forced her to study medicine but it was not a wise choice since she was of no use. Her sister from a different mother uses underhanded schemes to get rid of her. Out of guilt and frustration, she tries to commit suicide. Everyone thought she was going to die but she miraculously woke up.

Xiang Nuan starts to play this game because of a certain famous gamer. Later, however, she finds out that the game is much more interesting than the man…

- Description from Novelupdates