One Piece: Dream of Immortality - Chapter 493: Ex Marine

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.

When Coach Ethan saw Emma for the first time, he was attracted by her. It was a girl's breath. Emma is very stupid in learning to drive, but Ethan is very patient and let Emma sit on the coach to practice driving. This kind of close-up...

[Gunfight + case-solving reasoning + decisive killing]

“I’ve been black and white, and you said I was an undercover agent???”

When Dean woke up, he opened his eyes and saw the scene where the robbers were sharing the spoils.

Because of the confusion of the original owner’s memory, Dean mistakenly thought that he was a real robber, so he chose to eat black and white, and emptied the magazine with an American-style Juhe.

Just when he was about to take the money and leave.

A blond beauty came to the door: “Dean is an intern police officer. The bank in the town was robbed. I ordered you to investigate the suspect. You don’t want to fail your internship, do you?”

It turns out that I am an undercover agent!

Dean is numb…

- Description from novelbuddy

agreed. He thought they might just talk, have a few drinks, and that nothing significant would happen. However, she invited him to a hotel, and they spent the night together.The next morning, she told him it was just a one-night stand and that they would probably never meet again. She said goodbye and left. Ronan also decided to treat it like that.The next day, at his college's hosting club, Ronan was given the responsibility of hosting that year's annual function, where they had invited a singer.When Ronan looked up at the singer, he was shocked—it was the same woman he had spent the night with. After checking her history and social media, he formed an impression of her. Every picture she posted was in revealing clothes, bikinis, or almost nude outfits.He concluded that she was just a promiscuous woman, likely driven by lust, and that she had probably chosen to spend the night with him simply because she found him handsome.Understanding this, Ronan decided to focus on his work. That morning, she had made it clear that it was just a one-night stand and nothing more. He would treat it exactly that way and carry out his responsibilities.Protagonist has System---No NTRIt's Harem, with many girls but The Singer is Main Heroine.