That Person. Later on… - Chapter 63

Nidel, who belonged to the Technological Magic Order that held low prestige, became the bodyguard of a foreign prince behind the scenes. Left with no choice, he assumed the role of a bodyguard, turning into a black cat using the transformation magic he prided himself in, but the one who assumed the role as official bodyguard was the Royal Knight Legato. Nidel, who one-sidedly held feelings of affection towards Legato, thought of this circumstance to be interesting, butー

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 died at twenty-two—bitter, brilliant, and broken. But death wasn’t the end.Now, Noel wakes up inside a tragic fantasy novel he read long ago... as a nameless extra doomed to die before chapter five. But there’s a catch—this “extra” isn’t ordinary.Armed with future knowledge, a sharp tongue, and a magic talent that defies common sense, Noel won’t just survive.He’ll rewrite the story.Because in this world?The real genius never had a name—until now.