The supporting character's harem is very normal - Chapter 11: I have a plan (2)

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.

Ila, who had served the Empire for half his life, was decisively betrayed. He wanted to go to another country, but was almost killed on the run and then saved by the Dragon Lady Demon King.After crossing over, Ila, who had killed demons for half his life, was a bit scared, but...“Those who struggle with the evil dragon should be careful not to become the husband of the dragon...”“When you stare at the abyss, the abyss... offers a kiss.”Ila Elkaras was very confused.But the reality he encountered forced him to examine whether the abyss stood in the demonic world or... “The Empire of Light and Justice”

Ron finds himself reborn in the world of One Piece, stranded on a remote island in the East Blue. But he's not just any ordinary child—he’s bonded to a mysterious sign-in system that grants him powers with every new location he visits.At his first sign-in, he unlocks the legendary Sun Breathing Technique, along with a boost to his vitality. From Shitmotsuki Village to Skypiea, Enies Lobby to Marineford, Ron travels the world, collecting extraordinary rewards that make him a force to be reckoned with. The Raikiri, one of the 21 Great Grade Swords, Armament Haki, Observation Haki, and more fall into his hands.As Ron steps onto the battlefield of Marineford during the legendary Summit War, the mightiest warriors—Four Emperors and Marine Admirals alike—pause, stunned by his presence. But Ron merely waves them off, “Don’t mind me. I’m just passing through.”Join Ron on his journey across the Grand Line as he signs in at iconic locations, growing stronger with every step. This is not just an adventure—it’s a legend in the making.

Ed was transported into a world of Hunters, a harsh and extreme environment.In this world, winter days last only two hours, and even in summer, the daylight barely stretches to six hours!What makes it even more eerie is that when night falls, all creatures of various races turn into violent, frenzied monsters. Evil spreads everywhere, and the night itself becomes humanity's worst nightmare!Hunters, however, can only train through the Sunlight Meditation Technique, using the brief daylight hours to cultivate their strength.But Ed awakens the Moonlight Meditation Technique!From that point on, while others flee from the night, Ed thrives in it, growing stronger and stronger with each passing day!He slays dark sorcerers, exterminates vampires, and defeats the Wolf King!Gradually, Ed becomes the strongest human to ever exist!