Tada, Sore Dake de Yokattan desu - Chapter 2 - Nobody else Knows.

Leon a young man with the heart of a killer, did something unspeakable before getting transmigrated to another world.And what's more? He found out that due to a wish of his, he got transmigrated to the body of an incubus!And he got into the body at the worst possible time!Something happened, he managed to escape death and became the last of his race...he gained the Vice and Valor System,Lewd and immoral act could give Vice point while battle and bravery can give him Valor Point...This world has magic and beauties that none in his previous life can compare.Join the exciting journey of our MC as he gains immense strength and conquers the most gorgeous girls!

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.

Tomokui Kanata has been reincarnated into the weakest race, goblin, and given a new name, Rou, after having undergone an unfortunate death. However goblin Rou has retained his previous life’s memories, an unusual evolution, as well as being blessed with ability to gain status boosts from eating.

Luo Ling, an expert in the art of disguise, was bound to a System and was eager to begin his task.

As a result, before even successfully completing a mission, he got married!

At a 36 degree angle, Luo Ling sorrowfully looked up into space: “Tong’er, tell me, do I still have a chance to free myself?”

System: “… Your man is behind you.”

Luo Ling: “!!!”

The person who arrived, gathered Luo Ling in his arms, hugging him from behind as he said in a bewitchingly dangerous tone: “Based on your thoughts, it seems that I have not given you enough love. So let’s proceed in exploring ways to continue a new life.”

- Description from Novelupdates