The Reincarnated Assassin is a Genius Swordsman - Chapter 5

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.

Pirate World, Before the Summit War.Sengoku: “In this war, the advantage is ours!”Vice Admiral Tsuru: “Can we really win?”Sengoku: “We will win.”As the Summit War begins, chaos erupts on the battlefield.Above Marineford.Suddenly, Will appears in the sky with his crew, overlooking the entire battlefield.Sengoku: “What exactly are you here for? Are you planning to help Whitebeard?”“Don’t misunderstand.”Will scans the battlefield, his gaze sweeping over the powerful figures present. A hint of excitement lingers in his tone.“I’m only here for one reason—to kill all of you. That’s it.”Sabaody Archipelago.Will watches the Celestial Dragons strutting arrogantly through the streets, their eyes filled with disdain for the world. He can’t help but frown.“These are no ordinary Celestial Dragons… This calls for a heavy punch!”...Without hesitation, he throws a devastating punch, obliterating a Celestial Dragon on the spot, crushing the surrounding Marines and CP agents with overwhelming force.The survivors turn to a trembling communications officer clutching a Den Den Mushi and scream in terror:“Hurry! Notify Marine Headquarters! Call for an Admiral!”

Cheng Yan transmigrated only to end up in a medieval Europe like world, becoming Roland, a Royal Prince. But this world doesn’t seem to be the same as his former world, despite some similarities. Witches are real and they actually can use magic?

Follow Roland’s battle for the throne against his siblings. Will he be able to win, even though the king already declared him to be a hopeless case and with the worst starting situation? With his knowledge of modern technologies and the help of the witches, who are known as devils’ servants and are hunted by the the Holy Church, he might have a fighting chance.

Now, let his journey begin.

You take up a student career.

Student career upgrade to lv.7

Acquired skills: primary school knowledge, junior high school knowledge, high school knowledge.

You take the college entrance examination,

You got a perfect score.

Your basic occupation has been upgraded to lv.9, and the job transfer system has been activated.

You change jobs to become a scientist, you gain R&D skills

You use research and development skills to get space fortress construction technology

You use R&D skills to gain starship technology.

You are invincible.

- Description from novelbuddy