MTL - Gou Cultivates Immortals In the Chaotic World of Demons and Martial Arts - Chapter 121 The rain is coming (seeking subscription)

He approached her and announced domineeringly, “Ten million, you're mine!” Little did he know that she would smash his head and flee in panic! Five years later, for the sake of her young son, she endured humiliation and became his wife, always on guard around him, “Get out, what are you doing coming in?” His handsome face darkened, “Woman, you couldn't have forgotten that we are husband and wife, could you?”

Fear breaks the boundaries between dreams and reality, and it is impossible to tell which is reality and which is illusory. When the nightmare really comes, no one can be alone.

This is both a danger and an opportunity.

- Description from novelbuddy

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.

An 18-year-old girl who lost her family in an accident, Yamano Mitsuha falls off a cliff one day and transferred to a different world with a civilization level of medieval Europe. Mitsuha who discovered it was possible to go and return to Earth after a deadly fight with wolves decided to live in both worlds.

「For the sake of security in old age, I will aim for 80,000 gold coins!」

I will try not to let strange things circulate and distort the progress of the world, but I won’t hold back for the sake of my easy life and safety! While carrying three handguns along with words and deeds that appear decent, in her head, Yamano Mitsuha is a sly girl.

Making an effort to make money even with a small body that looks like a child to foreigners!

Oh, my secrets are too dangerous, you said? It’s fine, it’s fine! I’ll transfer away when push comes to shove!