The Runic Alchemist - Chapter 631: The Dark War 26

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.

Chen Rui, an otaku from earth, is reborn into a human body in another world, who falls into the legendary evil, brutal world of the devil called Mozu where humans are treated as food. He has to survive while facing horrors of the devil, violent dragons and a variety of power enemies depending on a strange super system chip and his wits. Surrounded by Devil’s beauties such as black-bellied lolita princess, cold queens, violent dragons, charming poisonous devils …

Wanting to live in the Devil’s world is hard! Wanting to live in the Devil’s world as a human is harder! Wanting a human to be the devil’s son-in-law is hardest!

Let us see how a small otaku uses power and strategy step by step starting from an ordinary human to writing a legend as the devil’s greatest son-in-law.

- Description from Novelupdates

An editor at the prime of her life—and with maybe just a little too much free time—finds herself waking up in one of her favorite RPGs with no clue as to what's going on or how to get back home.This might be the part where others rejoice over getting whisked away to a world of wizards and magic, but she certainly doesn't think it's anything to celebrate about.After all, she woke up in the body of a small-time villain with some severe personality issues.

The 27-year-old genius beauty doctor Xia Qing dies in surgery!She is reborn!She is reborn in the ward she’s most familiar with, in the body of a 200-pound pregnant woman—a woman who had died from pain during a Cesarean section due to her requests to not use anesthesia.She can’t help but worry about herself. This body was useless except for being young.How could Xia Qing tolerate this?On the menu are—revenge, losing weight, and snatching the idolized man of a scumbag girl in passing. Although she’s overweight, she strives to live well. Being overweight isn’t the end of days. They still deserve love.“Have you heard? Boss Pei has a child out of wedlock. He’s getting married!”“Who’s he marrying? Who?”“That 200-pound fatty from the Lin family of South City!”“Is Second Master crazy?”Lin Xiaqing turns her head to look. “You think I’m fat?”