Shinji Matou at Your Service - Chapter 899 - : The Greek Team Hurting Each Other

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.

“You’re the Demon King?”

In response to the woman’s voice filled with murderous intent, the man opened his mouth.

“No, I quit that?”

※ Demon King & Hero will show you the absolute limits of chaotic storytelling.

Rezen suddenly found himself transmigrated in the parallel earth where magic is possible with the help of Mystic Gems. He was excited to reach the top when life slaps him hard and gave him the lowest level of talent

Fortunately, Rezen activated his Farm System. So what if he does not have the talent for cultivation? His crops are more than enough to make up for the lack of talent!