My Seven Wives in One Body and Me, her Manager - Chapter 6: New Party and New Manager

Born crippled with a rare disease, abandoned by his indifferent father, and hated to the core by his half-siblings, Xylen’s life was nothing but a tragedy.His mother died searching for a cure, and the only person who ever cared for him was cruelly taken away.Betrayed. Schemed against. Left with no way out.Lured into playing Fallen Realm Online with the promise of earning money for treatment, he fought desperately, doing nothing but living in the game and failing over and over again—only to be killed by his half-siblings right before completing a crucial quest. His reward stolen. His last hope shattered.With nothing left to lose, he ended his own life in the real world… only to wake up on the day the game was released.Armed with future knowledge, Xylen vows to seize this second chance. He will become stronger. He will protect the only person who ever mattered. And he will make those who wronged him pay.But fate had other plans.Instead of a normal start, he is forced into a demon fief as a baron—with an uncle who wants him dead. If he fails to kill his uncle and defend his land, his character will die, and he will be permanently banned. Worse, he is given a race despised by both NPCs and players—and given a class that should not exist.A mystery, fearsome, and despised character to the world. Feared by gods and demons alike. A walking catastrophe in the making.Yet, the more he learns about his new power, the more he realizes…This is no curse. This is his greatest weapon.And when the world finally learns the truth about Fallen Realm Online?Xylenia will be the name that shakes reality itself.

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.

Apollo was a genius who was talented enough to achieve big things in his life, but because of a rare genetic disorder, everything came to an abrupt end.But when he thought everything was done, he again opened his eyes to another world as the baby of a noble family. Knowing that this might be his second chance, he decided to do everything he could to create a good and free life for himself.But surprisingly, this world is not simple, as there are beings with extraordinary power who can control the lives and deaths of others, giants who can crush mountains, dragons who can burn the seas, and many more. So now, to truly achieve his goals, Apollo needs to learn and adapt to this new world where life and death can be matters of thought.

Starting over once more, he has entered this “living game” again in order to control his own fate.

This time, he will not be controlled by others.

Previously the Level 200 Sword King, he will rise to a higher peak in this life.

Methods to earn money! Dungeon conquering strategies! Legendary Quests! Equipment drop locations! Undiscovered battle techniques!

Even the secrets Beta Testers were unknowledgeable of, he knows of them all.

Massive wars, life advancement, entering Godhood, sword reaching to the peak; a legend of a man becoming a Sword God has begun.