The Extra's Harem In Dead End Game - Chapter 11: Turkish Swordsman

Hakuto's life changes forever when his father Shin— a man with highly questionable morals—marries Kagura Kurotsuki, the CEO of a multinational company, and they move into her luxurious mansion.There, he meets the alluring daughters of his new stepmother: the seductive Yuzu—who doesn't hesitate to tease both her new stepbrother and her stepfather in ways that are... rather bold—and Rika, more introverted and irritable, yet just as sensual.But nothing is truly as it seems...Kagura is a succubus, but Rika and Yuzu are different.They were born from a demon and a vampire—something that shouldn’t be exsiste.Because of that, demons, vampires, even humans want them.But Hakuto won’t allow it.He’ll never let anyone hurt his beloved stepsisters.

Entering Tokyo in the bubble era, in this strange era, the only familiar ones are Matsuda Seiko, Nakamori Akina, Kudo Shizuka…

- Description from novelbuddy

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.

While the demons were rising, mankind was about to become extinct. Six temples rose and protected the last territory of mankind.