His Dark Desire: Tales of a Yandere - Chapter 177

Han Yun was spoiled from childhood.

He survived past his emperor dad and crown prince elder brother, and became an emperor.

He didn’t know how to govern the country, but he was lucky—there was a Grand Preceptor who “assisted” him, spoiling him even more than his father did.

After just a few years, this puppet emperor died. When he awakened, he had transmigrated into the modern world, becoming a third-rate model struggling alone without any loving parents.

Just when he thought he had become a little cabbage that nobody wanted and no one would ever spoil him again, a certain ancient monster of a Grand Preceptor who had lived 1,000 years appeared again… and looked to be doing quite well for himself.

The utterly impoverished little emperor had tears in his eyes: “Beloved subject! Zhen (royal We) have missed you so much!”

Grand Preceptor: “Your Majesty, this minister has waited for you for a thousand years.”

- Description from Novelupdates

When Fang Jin learned that he was in a cultivation novel where the protagonist was a lady and that he had become cannon fodder, he quickly racked his brain to think of a way to save himself.

Everything seemed wrong until he saw it.

[First day as a pet owner.]

[Attractiveness +1]

…

[A day of cultivation with zero gain.]

[Understanding +1]

Kazura was selected as the winner on a lottery that he bought on a whim and received ¥4,000,000,000 (4 billion yen).

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.