Elf Tensei Kara no Cheat Kenkoku-ki - Chapter 11Book 2: -1: Lucy and Kuu

“You’re not taking me to bed. Ever.”

When gods gather, lightning will strike and the earth will move. Immortals! Which of the numerous way to immortality should one follow? Immortals are hard to seek, but why should immortals hide? Heaven has no mercy, but humans have emotions, and these emotions hinder the road to longevity!

Train the inner self to stay calm, train the external body to be resistant, then cross the three continents and four seas alone, and fight valiantly with demons and devils! With the heavenly baton in hand, raid the devils and demons without any resistance! Take one step to cross nine stars and chase the sword in the dreams! Traverse a thousand li of river and mountains in a single day! The exceptional beings do not mix with the ordinary! Within the universe, where can one find an obstacle! Moving like a dragon, with talent like a phoenix! The heavenly Daos and stars will guide one’s way!

- Description from Novelupdates

(Third Person Limited PoV.)Betrayed by his fiancée, mocked by his siblings, and disowned by his family—that was Lev’s fate.Even when he regained memories of his life on Earth, where he realized that his world was strikingly similar to his favorite novel, it still didn’t help him change anything.How could it be?Because the protagonist of the story had already achieved his happy ending—gaining a beautiful wife and living a blissful life. Meanwhile, the world continued to move forward.What do people usually do with a novel that has ended? They tend to stop caring about the world within it, even if it falls into ruin, especially if the novel isn’t particularly popular.The world Lev Razanov lived in shared a similar fate—it was destroyed.[Hero’s System successfully installed.][Critical condition detected.][Do you wish to return to the past?]Lev was given a chance to return to a time when the story of his favorite novel had just begun.Although he was destined to become an extra villain—a pawn of the pawns serving the real villain, he vowed to end the lives of anyone who had caused him suffering: his siblings, his fiancée, the main character, or anyone else.[Hero’s System inherits your desire from your life on Earth—the desire to do good.]“Who said killing your enemies is an evil act?”

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.