Immortality begins with Becoming an Alchemy Grandmaster - Chapter 321 - 161: Rich Spirit Land, This Time Is

Hiro was your usual Hentai-addicted NEET. One day after his house was robbed and he was killed, he was reincarnated as a lewd worm. join his adventure as he finally realizes his dream! becoming a tentacle that could pleasure women!

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.

A short, happy, and heart-warming story about the daily lives of a modern-day married couple.