Na-Isekai Ako - Chapter 13: Support

Bai Aoxue, the best mercenary in the 21st century, is accidentally sent back to the Chengxi Dynasty in Great Continent due to an explosion in her mission, and trapped in the first daughter of Prime Minister. After her rebirth, she is set up by her father to marry the 5th prince Jun Yeyan who wears a mask all day long.
In the face of bloodthirsty enemies, discord between brothers, collusion among courtiers and invasion of enemy state, can Bai and Jun resolve the crises? What will happen to their political marriage? How will the fierce battle for the throne end?
With many twists and turns, the book brings you to experience palace revolution, love and hatred thousands of years ago.

- Description from Novelupdates

A swordsman hailed as the strongest has reached his end, and was reborn as an elven girl.

This is the story of the swordsman only knowing how to kill in his past life aiming to be the best healer as a girl.

In the final battle against a monstrous entity with his teammates, the strongest swordsman, the Hero’s mentor and the only one in their party incapable of magic yet the most skilled with the sword, sacrificed his life to end the battle once and for all. Reincarnated as an elf girl, the strongest swordsman decided to live a different life from his blood-stained past and pursue the magic that he has never used before.

As a girl, she apprenticed under the old potion maker and healer of the village to be like someone she had admired in her previous life while keeping her condition sharp with sword training as she had done in her past life.

After learning the ways of a healer and convincing the elf village that she is capable enough of leaving for the outside world, she hitched a ride with a party of adventurers passing by the village and went out to see how the world has changed.

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.

(A cruel, merciless, inhuman, Prime Minister gong x (previously) a cute, naive, foolish prince shou)

As an alluring beauty, the Ninth Prince Qi Changyi inherited his mother’s looks, but was unfortunately a bit s*upid. Not only did he live in fear, even within palace walls, but he also merely lived as a substitute in his beloved’s eyes. Then, while being used and tormented, his delicate, pure heart finally burned to ashes.

Pei Zheng was the Prime Minister of the Imperial Court, a man of great status; he gained it all through the most ruthless methods. He was known for his cruel nature, but gradually, he became close to the unfavored ninth prince.

“Your Highness, just now, at court, who were you looking at? Huh?” Pei Zheng squeezed the small man’s delicate little chin.

Qi Changyi’s eyes were misty with tears of pain, “I, I wasn’t.”

“Stop trying to seduce others.” Pei Zheng’s voice was frigid. “Otherwise, I’ll make sure that General Zhao, for whom you pine, dies on the battlefield!”

He thought he had a firm grip on this little fool, but he could’ve never imagined that one day, this little fool would leave his side carrying a broken heart.

“Brother Pei, I’m leaving now, you should be happy.”

With scarlet eyes and a heart burning with obsession, he searched everywhere, but found no trace of him.

“I won’t, without you, I’ll never be happy again. Your Highness, where should I go, how can I bring you home?”

1v1, happy ending! But the path leading up to it is laced with sweetness and cruelty.

- Description from Novelupdates