MTL - Global Beast Taming: My Battle Pet is Double of Others - Chapter 725

A normal office worker, Toru Minasuki, was swallowed up by a dimensional fissure and reincarnated into a different world. Upon reincarnation, Toru was given a [skill board] by God. Make the most of it to acquire all the necessary skills! Even though he is an “inferior person,” he’ll make his way to the top!

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.

Suddenly, the unmarried twenty-year-old Ye Zhizhou had many more relatives, yet it was too late for him to clearly understand the circumstances as he nearly died in a car accident. After that, he somehow managed to survive and was even forcibly bound to a Salvation System.

How is it salvation?

Harems destroy worlds! Preventing a harem will save them!

. . . .

Ok, prevent harems. After seeing the entire system introduction, the corners of Ye Zhizhou’s mouth twitched. In order to return home safely, he decisively began his risky journey—he’d just treat it as if he was playing a large-scale strategy game.

Since then, the people the protagonist would rescue, he rescued first.The businesses the protagonist would make, he made first. The little brother the protagonist would take in, he took in first. The cliff the protagonist would jump off of, he jumped off of first. The gay s*x the protagonist would have, he’d have. . . . Wait wait, can’t do this one, change it, let me change it.

???: No, you can do this one.

Ye Zhizhou (alarmed): Who’s speaking?

???: Your husband.

Ye Zhizhou: . . . .

- Description from novelupdates

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.