I, Am a Living Yama, Empress Advises Me to Stay Calm - Chapter 115

Wang Cheng: Boss Chu, I think my mom will not agree two hundred percent with our affair, so I have a once-and-for-all proposal, do you want to hear it?

Chu Yifeng: Let’s hear it.

Wang Cheng: It’s very simple, why don’t we break up and not worry about anything?

Chu Yifeng: What you said is quite reasonable, but we can discuss this matter further in the bedroom.

Wang Cheng: …I’m just kidding. Look at my sincere face. How could I break up with you?

Chu Yifeng: It’s too late.

- Description from Novelupdates

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.

Being a nobody from a poor district of the Federation, Nick is a sixteen year old boy just trying to find his place in the world. When he finally gets his shot to enter the Beast Domain upon turning sixteen, he jumps at the opportunity to finally make something of himself — to carve out his own future.His goal? Survive. Hunt. Earn enough money to finally support his little sister back home and bring them out of poverty.But to a naïve young boy like Nick, the world is far more sinister than it seems — leaving him no choice but to adapt or die.To a poor young man like Nick, though, there was only one choice he could make.Follow Nick as he navigates these obstacles and carves out a future for himself and his sister, all while uncovering the various mysteries that shroud his worldview in darkness.