Avoid Yandere Constellation - Chapter 146:

Just before being summoned to another world, the protagonist’s summoning medium was secretly swapped by someone. As a result, he was not summoned as the “Holy King” but instead as the “Sex King.”The magic he can use includes water magic in the form of lotion, fire magic as candle wax, and his summoned beasts include a wooden horse used for punishment…Branded as “vulgar,” “useless,” and “filthy,” he is rejected, has his engagement annulled, and is ultimately exiled. However, the one who picks him up is a princess from a nation where the sex industry is legal.Using his modern knowledge, the protagonist begins rebuilding the nearly bankrupt sex kingdom. He introduces new fashion trends unknown to this medieval world and uses his authority as the Sex King to subjugate the girls. He then establishes modern sex service techniques.The protagonist's method of leveling up is through intimacy with his heroines (his concubine maids). The more intimate he gets, the stronger he becomes, and the wealthier the kingdom grows.However, the surrounding great powers will not stand idly by and allow a flourishing nation full of women. Thus, the flames of war are ignited.Utilizing his creativity, adaptability, and cunning, the protagonist repurposes his sex-related magic for military applications and overwhelms his enemies.As he gradually awakens to the path of conquest, he begins walking the road of a ruthless emperor. However, by his side is always a heroine, a celestial beauty who keeps his heart from straying too far…

You boiled two eggs, Culinary skills +1.

You chewed a mouthful of cereal, your jaw is strengthened.

You are riding a bicycle, driving ability +1

you gazed at the beauty, your mood is very pleasant, your kidney function has been strengthened, Appraisal ability +1.

You see elderly women dancing in the public square, you can’t help but want to swing with their rhythm, dance skills +1.

You glanced at the newspaper, your reading ability is strengthened, knowledge experience +1.

You sneezed, your disease resistance has improved.

You took cold medicine, toxin resistance is improved, medicine proficiency +1.

You observe nurse use injection, your basic medical skills are strengthened, medical skills +1.

…… I don’t know what’s going on, my strength is improving even if I’m drinking cold water. I don’t want to stop, but I’m so worried…

- 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.