Harem Startup : The Demon Billionaire is on Vacation - Chapter 417: Passive Income with Emotional ROI

​The world, Earth, was devastated by the Great Incursion, an apocalyptic invasion by dimension-hopping monsters. Humanity's only hope now lies in Galaxy Fall, a newly accessible parallel world where they can gain strength through a System of quests and missions.​Five hours after the Invasion, the betrayed survivor Mirabella is mysteriously reborn and gains a unique power: the [Master Account System].Her initial skill is the deceptively simple but devastating 'Multiplier x100', which applies a 100 times buff to all her offensive capabilities, including physical attacks, spirit energy skills, and damage-over-time effects.​Mirabella must now transform from a silent survivor into the world's most feared warrior, who was only scared of one thing, which is?“I Hope I don't run out of opponents in Both worlds.”

The worst student of Westroad Academy. The disgrace of the Blake House. A new soul enters the body of Frey Blake, who couldn’t overcome his miserable life and chose death instead. “What’s with this body? I’ll have to work on tuning it from scratch.” The Great Mage Lucas Traumen, with the body of Frey Blake, gains a chance at revenge!

Seria, a social outcast, has changed.
Seria Stern, the wicked woman who made everyone tremble with fear, was now calm.

In fact, she wasn’t just changed, she was a completely different person.

The moment she realized that she had possessed the body of the villain Seria, in a romance novel, she had a hunch about the future and decided to live low.

She would avoid kidnapping and harassing the original heroine, hence preventing her death by decapitation at the hands of Kalis, the second male lead.

In order to avoid that, she had to fix her bad relationship with Kalis and even healed his injured arm.

Thanks to that she got engaged with him, so it’s all worked out.
Finally, the original heroine returned, and her husband, Lesche, should be on good terms with her now.

“I’ve been waiting to escort her, so…”

Lesche asked, resolutely cutting off Kalis’ words.

“Miss Seria, it would be better for you to choose. With whom would you want to go with?”

Something was strange.
The original, wasn’t it perfectly fine?

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.