Urban Harem God: Harem With My Ultimate Copy & Paste System! - Chapter 4: Jayden’s Past Reality

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.

“Go Yohan, you really are a terrible bastard.”“I can’t help it. Bullying is more fun than being bullied.”Despite his outer appearance of a kind model student, Kang Jun was filled to the brim with an inferiority complex.As he advanced into his second year, he grew closer to Go Yohan, who was in the same class as him.“I’ll treat you especially different.”At some point, as if it were only natural, Go Yohan claimed his seat at the very summit of the pyramid inside the school.He, whose second nature seemed to be ignoring and suppressing others, showed interest in Kang Jun.Kang Jun, who was subtly ignored by his friends for being weak, didn’t dislike Go Yohan’s interest, but…Eighteen, the period where one’s pride took the lead and held fear of crossing the line.Kang Jun had to make a choice to survive.A very wise choice.

Kael was once a being so powerful even the gods feared him—until he was thrown into The Null, a realm of endless torment and eventually cast into inexistence. But he returns, reincarnated as a powerless beggar in a broken world ruled by monsters and corruption.With memory of godly blood on his hands, he is determined to reclaim his strength, survive the Nexus's deadly trials, and tear down the heavens themselves.But it's a matter of time before the gods and celestials know he’s returned. And this time, they will not make the same mistake twice.> ◇ Ravager (Rank E) Eliminated. 20 VRP Gained.> ◇ 0.00109% Memory Unlocked. Forgotten Technique: Blight Shield Relearned.> ◇ Ather'valis, The God-Killing Blade, has been acquired.

The story is about a a hitman, Who dies because of his own recklessness and transmigrates into a game he used to play after his retirement as a hitman.I'm not gonna spoil any further, but i might answer few of your questions.Is MC overpowered?Nope, he'll become strong over time and all battle he'll fight will be because of his effort and techniques.Is there magic and adventure?Yes! It have both magic like normal isekai with adventure and fighting with monsters and many other things. There are other important things like “Essence Stone” But let's talk about it in the chapters.There will be harem?Not really, He will be in contact with many beautiful female and males but one waifu but i haven't decided yet.All i can say is, give it a try, I'll try my best to make it worth your time.