I’m a Villainess but So Popular - Chapter 143: Side Story 5 : Autumn News

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.

The mortal body, metamorphosis, longevity, immortality, and eternal life. These five realms, step by step, reveal themselves in front of you. As a normal person, how can one try step by step to reach and open the door to eternal life?

Between the heaven and the earth lies the mortal body, the mysteries of metamorphosis, freedom of longevity, the power of immortality, and the hope of eternal life. A story filled with endless new magic, a new world of immortal styles, people, demons, gods, fairies, magic, kings and emperors. A world of love and hatred, revenge, and mystical battle, all in “Eternal Life.”

- Description from Novelupdates

There are times when all it takes is the right voice to help you realize the greatness within to conquer the painful evil without. Uzumaki Naruto's voice of promise turns out to be his... from the future.

Hace 24 años, el mundo colapsó. Un virus conocido como Eclipse transformó a la humanidad en criaturas mutantes, llevando a la sociedad al borde de la extinción. Las ciudades se convirtieron en ruinas, los asentamientos luchan por sobrevivir, y la verdad sobre el origen de la infección se ha perdido en el tiempo.En este mundo roto, Kai, un viajero solitario y mercenario de intercambio, sobrevive negociando Obsidianos, la única moneda de valor en la nueva era. Su vida cambia cuando cruza caminos con Lía, una misteriosa joven perseguida por mercenarios. Su única posesión es un antiguo colgante de Obsidiano, cuyo secreto podría cambiar el destino del mundo.Juntos, se ven envueltos en una conspiración que los lleva hasta el Laberinto Ancestral, un lugar prohibido que esconde la verdad sobre el Eclipse. Perseguidos por un ejército liderado por el despiadado Voss, enfrentándose a infectados más allá de la comprensión humana y descubriendo que su pasado está conectado al desastre, Kai y Lía deberán decidir si la verdad merece ser revelada… o si es mejor que permanezca enterrada.Cuando la última puerta del Laberinto se abre y los ecos del pasado despiertan, solo una pregunta queda en el aire:¿Es el Eclipse el fin de la humanidad… o su evolución?