Seirei Tsukai no Blade Dance - Volume 18, Chapter 2 - Sacred Maiden

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.

After crossing into the world of Doraemon, he became Nobita.

With an invincible treasure bag, the life of a primary school student is simply boring.

I am preparing to let Shizuka grow up as soon as possible, so that she can marry and go home as a daughter-in-law.

【Ding! You have joined the chat**]

Astronaut Liu Peiqiang: “The sun is about to explode! Who will help me if I give out 200 points~”

“Enlarge the flashlight, shrink the Earth, or shrink the sun and throw it away~”

The richest man, Iron Man: “There’s a purple potato monster who wants to kill half of the universe! I’ll give out all my wealth! Come and help!”

“Time stopper! You can stop the time in the entire universe, and you will kill him again! Perfect!”

“Well, is the time stopper used to kill people?”

“Can you lend me this thing?”

“I have a bold idea!”

“+1”

- Description from novelbuddy

Reincarnating into the world of Jujutsu Kaisen, he became Gojo Satoshi, the twin brother of the strongest sorcerer, Gojo Satoru. That should mean he’s destined to be the most powerful Jujutsu sorcerer, right?Unfortunately, fate had other plans. Nearly killed by Satoru in the womb, his cursed energy was devoured before he was even born. But at that moment, he awakened the [Shinigami Fusion System].Since he couldn’t become a Jujutsu sorcerer, he would forge a new path, a Shinigami with Heavenly Restriction!Thus, Gojo Satoshi, born without cursed energy yet possessing the legendary Six Eyes, became the true nemesis of Jujutsu sorcerers.

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.