After rebirth, I rejected the rich yandere lady - Chapter 1 - : It’s easy to latch onto a rich woman, but hard to live off her charity.

One day every human on the world suddenly receives a mail claiming to enact the World Salvation Project. Half in doubt Kurosaki Shion, a diligent university student and loner, follows the mail’s instructions, becoming one of a million Demon Kings governing his very own Domain in the new world.

*** This is a post-apocalyptic story containing many fantasy elements. It is a somewhat dark tale following Shion as he grows while aiming for the unification of the all too sudden new world. It has many game-elements bolstered by strategical thinking while at the same time providing funny moments and romantic encounters.

My crew? Yeah... it's a little special.First Division: Night Raid from the Akame Ga Kill.Second Division: The Akatsuki, led by Pain, from the Naruto world.Third Division: The Seven Deadly Sins.Naval Headquarters:“Everyone, be on high alert. That man... he's coming.”Four Emperors:“Sh*t, who the hell provoked him this time?!”“Someone get ready to apologize. I’ll go in person if I have to...”The Dragon Hunting Pirates — a name that makes the entire world tremble!

Otaku Lin Fei crossed over to a new world…

Rare and exotic medicinal pellets? I eat them like snacks…

Powerful martial art secret instruction manuals? I can sell them like newspaper bundles…

What..You’re an absolute genius? I wreck geniuses like you for a living…

Why am I so powerful?

It’s because I have leveling system version 1.0!

- Description from Novelupdates

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.