Former General Is Undead Knight - Volume 2, Chapter 33: Earl Mansion’s Raid?

What happens when a scientist from a futuristic world reincarnates in a World of Magic and Knights? An awesome MC is what happens! A scientist’s goal is to explore the secrets of the universe, and this is exactly what Leylin sets out to do when he is reincarnated. Dark, cold and calculating, he makes use of all his resources as he sets off on his adventures to meet his goal. Face? Who needs that… Hmmm… that guy seems too powerful for me to take on now… I better keep a low profile for now. You want me to help you? Sure… but what benefit can I get out of it? Nothing? Bye. Hmmm… that guy looks like he might cause me problems in the future. Should I let him off for now and let him grow into someone that can threaten me….. Nahhh. *kill*-

Alternative: Leylin is transported from an advanced technological era into a medieval world— except there’s magic. Equipped with “only” his quick wits and an A.I. chip fused to his soul, he sets out to become the most powerful magus the world has ever known. In a land divided into the Light and Dark Magi, the weak can either be cattle or disposable slaves. Only the strong can determine their lives, and only they have the luxury for virtue. Yet strength is only a tool for Leylin, like any other. His goal, in the end, is his own.

A master assassin transmigrates into an interstellar era.

Other players were responsible for competing in the e-sports arena, while he was responsible for stringing up and beating up the other players.

His sword was hidden during the peak of day, and he was a gentleman who arrived in a flash of light;
As a vanguard of the eternal night, he was the variable between life and death in the world.

“As you know, the Star League’s difficulty levels are arranged in this way:
Paradise < Simple < Normal < Difficult < Nightmare < Hell < [Tyron Odin]”

- Description from Novelupdates

The Hero of Light that saves the world.The Demon King that plunges the world of darkness.Which one will you be?“I'm both and the Great Sage, the Barbarian King, and everyone else while I'm at it!”

“The lifespan of a butterfly is between three days and a month, and most butterflies only live for a week.”
“Like them, I have only a few months to live, maybe less.”

–

The first time Hu Die met Jing Yu, he thought she was a world-weary girl who committed suicide.
The second time they met, he told Hu Die indifferently: “If you jump down again today, I’m not saving you again.”
Later, she told him: “Jing Yu, don’t feel sorry for me.”

Later, Jing Yu returned to the arena and won the glory that belonged to him.
Under the flashing lights, he suddenly remembered the girl’s voice, and said a nonsensical remark in front of thousands of people.

——”I’m not sad, I just think that at such a moment, it would be better if you’re here.”

“He is a whale swimming in the ocean. One day, a butterfly inadvertently broke into his frequency. That was the most beautiful moment in his life.”

- Description from Novelupdates