MTL - The Villain’s Younger Sister - Chapter 6 number 6

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.

Life is unpredictable. Her husband loved her stepsister, deposed her as Empress and even forced her son to death. In that Cold Palace, she was forced to drink poisonous wine. So in the next lifetime, she made a promise to never do good deeds and help others, to never step into the palace and to never become the Empress!

At the Prime Minister’s estate, the mistress’ daughter is reborn into a she-devil.

An evil stepmother? I will make sure you go to Hell!

A two-faced, hypocritical older stepsister? I will rip apart that beautiful façade!

A scheming younger stepsister? I will throw you into the grave!

You guys didn’t let me live peacefully so you should also expect the same!

Initially she wanted to stay away from disaster as far as possible; however, a man’s heart is like a needle in the sea—impossible to search for, impossible to understand.

The man who once swore to abandon her became someone who can’t live without her.

The enemy from the past lifetime suddenly confesses his feelings for her.

Even worse, she is bothered by a handsome man with a thick-skin who doesn’t know how to give up!

- Description from Novelupdates

In her past life, she was his personal physician, his junior,Due to the age difference, she could only bury her love for him deep in her heart.An explosion awakened her, and she found herself back in his era.When they met again, he was the noble and aloof scion of his family,She was a village girl with a tragic background.But this time, she would not shrink back,She would bravely pursue her love, making this second chance at life devoid of regrets.In public, he was cold and ruthless,In private, he was a devoted lapdog to his wife,His maxim was, “What the wife says is always the truth.”This story is a one-to-one relationship, with both parties being virtuous and strong.

The protagonist, Punk, is a cautious, cold-blooded, and ruthless Mage.

His goal is always his top priority, over feelings or morality. When unnecessary, he doesn’t like to act like pigs to eat tigers; there are almost no life and death struggles, sometimes risky but steady progress. No strong enemy everywhere, Instead, Punk is always a strong enemy of others.

And he has a very keen interest in the secrets and teachings of the Netheril civilization.