Amukelo: The Burdened Path - Chapter 11: The Burden of Hope

Traversing into a Fantasy World, Watson became the youngest son of a run-down baron, ranked eight in the family.

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.

Junseo thought he was just installing a chill farming sim to de-stress after another soul-sucking shift in Seoul. Grow some crops, raise a few cows, maybe romance an NPC—simple stuff.Then he woke up inside the game.In a new body. In a suspiciously sexy world.With a system that thinks “breeding” is more important than breathing.And a robot waifu guide who takes everything way too literally.Now he's stuck in a countryside hellhole with zero skills, zero tools, and a suspicious loaf of bread. His only goal?Survive without accidentally triggering a hentai side quest.Too bad the game has other plans.Too bad the villagers are way too friendly.Too bad the only way to unlock skills... is by combining everything.He just wanted to grow carrots.Now he might end up marrying half the village.Tags:Transmigration,Harem (slow burn),Comedy,Slice of Life,Farming Sim,Adult Themes (18+),System,Self-aware Protagonist,Kingdom Building,No Overpowered Skills,Robot Waifu,Skill Fusion and Lewd but Smart