Paladin of the Dead God - Chapter 6:

He said I was the most despicable woman he ever met…

In order to love him, I lost my family, and become an imprisoned tool used for his vengeance from a noble lady. Everyone said I was the daughter of a rapist… I cautiously maintained the excruciating deep love for him and suffered from mental and physical exhaustion…

I thought someday my love would touch him and then I would live a happy life just as a fairy tale, but in fact I fell into an eternal nightmare…

The poor Commandery Princess is down and out. Her father died when she was young, and her mother passed away not long ago. Her grandfather, the only one she can rely on, is now at death’s door from his illness. Faced with the merciless uncle, the greedy aunts, as well as cousins competing to present the model of the worst relatives, the Commandery Princess could do nothing but feel depressed in heart.

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.

Vergil, a 21-year-old young man, leads an apparently simple life in a somewhat troubled world. His family is also simple—although his father is no longer alive, his mother has always been by his side, despite being a bit... aggressive. But that's not so unusual nowadays, right?Everything changes drastically when Vergil, after an unexpected death, awakens as a demon. To his surprise, he discovers that he has accidentally married beautiful Pure-Blood demonesses.Now, he will discover how the world really works from a Demon's perspective.