I Refuse to Become Scumbag in Tokyo - Chapter 8: Decision 1

The chief female forensic investigator, Ran Yan was secretly killed by her assistant. Unexpectedly, she was reborn in the years of the Tang dynasty. After experiencing a narrow escape, she fled from Jiangnan to Chang’an. Although, Chang’an was at the beginning of its flourishing period under the Li family’s Tang dynasty, various princes were vying for the throne by using all kinds of strategies. This was the dark days of the imperial court, where one needed to walk on a tightrope as one’s life was as powerless as an ant. The Xiao family controlled a large amount of wealth so inevitably they also became involved in the conflicts.

After arriving in Chang’an, she discovered many suspicious incidents: the original owner had unexplainable amnesia but his family was indifferent. She once again saw the orchid shaped clay inkstone, a valuable object that her mother has given her in modern times. Hence, could it be that she can time travel back? In order to survive in the Tang dynasty, she displayed her strong spirit and willpower by learning medicine from a doctor, pretended that she benefited from being sick on how to cure diseases, suffered hardship in earning money, manufactured penicillin, cured syphilis, and used her autopsy skill and experience to solve each and every murder mysteries.

- Description from Novelupdates

I exist in the darkness, disappear under the bright light, and will eventually devour the sun and turn into the shadow of all things… Known by people as the indescribable terror of darkness; the king of shadows; the dark day; the existence of the shadow of the world , is still just a somewhat special high school student, facing a weird death game…

- Description from novelbuddy

Matthew, a 25-year-old otaku, never imagined his obsession with fantasy worlds would turn into reality—until a fatal gas leak ended his life and transported him to another world.But this wasn’t the second chance he hoped for. Born as the illegitimate son of an affair, his very existence was a stain on his family’s honor, and his father relentlessly sought to kill him.Yet Matthew, now Claude, survived, again and again, driven by an unyielding will to live.Until one day he discovered his power darkness. Feared and reviled in this world, dark mages were hunted and burned alive.Knowing his gift could become his downfall, he trained in secret under Theo, his true father.When he turned sixteen, he, his mother, Dalia, and Theo planned their escape from the small town.But their attempt was thwarted by knights and clerics from the Promised Land.Though he narrowly escaped with his life, the cost was high—his family’s safety shattered.Wounded and desperate, Matthew fled to the fabled Elysian Plains, the last hope for those like him.Just as he reached the border of the Elysian Plains at eighteen, an ambush left both him and his mother gravely injured.Collapsing on the sacred ground, he heard a voice echo in his mind:[Welcome to the Elysium of Darkness System, Lord of Calamity.][Your first quest is available!][Increase the number of dwellers in the Elysium using your seeds and blood! Spread your legacy by making demons and witches bear your children!]

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.