MTL - Manga Guidebook - Chapter 102 Need for relatives

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.

In a world of magic, monsters, and rising heroes…A quiet young man with a simple life finds himself walking a path far greater than he ever expected. With his axe in hand and peace in his heart, he'll discover strength where others seek power.Slow-burn growthParty bonds & adventureUnique class & stat systemA journey that starts small—but won’t stay that waySometimes the strongest warriors are the ones who never wanted to fight.

The happiest thing in the world is to be able to amend what you have done wrong. She who acted willfully because of a game, was reincarnated into a time when she still had her parents’ love.

For the sake of her family, she began her life as a pro gamer.

But this time, she was no longer the Human Sorceress that she was familiar with. She was an Elven Huntress. Could she still acquire the power to be the Right Hand of God?

- Description from Novelupdates