Fairy Tale Chronicles - Volume 5 Chapter 2.1

In an era when the power of Fire Magic was considered to have reached its limit, one girl began researching nuclear fusion.

She is the twenty-fourth century’s strongest immortal cultivator, but transferred into a world of magic where demons roamed rampant; a punching bag tyrannized and ostracized by her clan on one side while the scum of a man that is her fiancé humiliated, trampled her on the other side…

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.

After breaking up with his girlfriend, he accidentally acquired a genius system and rose from there against the heavens, becoming invincible..

- Description from Novelupdates