MTL - Spiritualist In Korea - Chapter 499 awake

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.

The protagonist transmigrates into a novel and gains a system where they grow stronger by simply writing in a diary.July 7th, sunny: “The boss’s outfit is hideous again. Wouldn’t it be better to wear something cooler?”July 7th, evening: “I’m about to have my engagement called off. So excited! How should I act?”July 7th, evening: “Lin Qingyue, the female lead, is probably going to drown her sorrows in alcohol.”The protagonist thought it would be easy—just jot down daily musings, record life’s events, and earn rewards. All while playing the part of a villainous, bootlicking second-generation rich kid, moving along with the original plot.But unexpectedly, the female leads gain access to copies of the diary entries.One by one, they stop following the script, and the plot spirals completely out of control.July 10th: “The female boss is an idiot—no one would want her.”Soon after, the protagonist gets punished at work, all because they entered the office with their left foot first.

She had a lifetime of fake virtue without receiving a virtuous ending. In the next lifetime, she controls fates with the flip of her hand. To the jerk who wasn’t faithful, she’ll draw a premature death talisman for him. For the poisonous step mother, she’ll send a death flower. For the step sister who is two faced, she’ll personally rip off that fake pretty face!

But when she personally offered up her body to her nemesis because of a child who she had no fate with, something unexpected happened. The night of the big wedding, the groom changed and a cold and luxurious man pushed her down. “You can marry whoever you like, but you can only give birth to my children!”

- Description from Novelupdates

The world is big, but I am the only one who is orthodox.Sweeping the world's immortal sects with the power of the Celestial Dynasty.A strong man who practiced the 'Way of the Emperor' came to a world full of immortal sects, and a secular dynasty that was despised by the practitioners gradually came to be on an equal footing with all the top immortal sects.The law of the dynasty is that everything in the world is the king's land, and the shores of the land are the king's ministers! There is only one orthodoxy in the world, and all immortal sects are illegal organizations!