Tensei Shitara Slime Datta Ken (WN) - Chapter 363

In a Fantasy world in which a young girl with the Divine Protection of the Hero battles against the Demon Lord. In that world, Red, the elder brother of that young girl Hero, possessing the Divine Protection of the Guide which only grants a high initial level, fought in the initial party of the Hero.

[Ding! The host is about to die socially, the Goddess Conquering System is activated! ][Binding successful! ][Rebirth begins! ]----What Happened wasn't i caught masturbating, how could i rebirth?“System, Introduce Yourself”----[Goddess Conquering System Activated!][Main Strategy Mission Unlocked!][Target – Clara Mackerel][If Clara violently resists or if you experience social death after being intimate with her, it will be deemed a failure, and you will restart.][Upon completing the mission, system rewards will be given]----“System, do you have any other functions? Is there a beginner's gift package?” Harry asked expectantly.[This system only issues Goddess Conquering missions and rewards for completing those missions.][In the event of failure, the system will select a time period for the host to rebirth.][Other functions must be discovered by the host.]

Fate and destiny; no one can foreshadow the terrifying challenges on the road to the Pure Land. Instead, one may unearth the evil within the road of light towards paradise.

A King’s Holy Sword, bringing light to the darkness,

An unyielding soul, igniting the fiery hope of the world,

As his soul awakens, the youth fiercely battles the gods of darkness and evil,

As the surging dark clouds gushed out like a phantom, their conflict swept the world like raging tide!

The clash of darkness and light, a massive war on the verge of exploding,

The decisive battle of gods and deities rewrite the creation of the world into one destructive epic!

- 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.