The supporting character's harem is very normal - Chapter 502: Angry Barosik – Arine’s plan

Su Yao passed through and traveled to the Marvel world to become a mutant. He was still in the experimental base. He expressed a little panic…

Fortunately, at the critical moment, the mutant ability ‘imitation’ was awakened to imitate the opponent’s ability!
…
Imitation object→Orochi (title: Sun God, Will of the Earth)
Imitation object→Wanda (title: Scarlet Witch, owner of chaos magic)
Imitation object → Sun God…
…
Professor X: “We must find him as soon as possible and guide him to control his power to avoid causing irreparable disasters!”
Magneto: “You are my child???”
Thor: “Brother?”
Loki: “?”

- Description from novelbuddy

“My name is Shun Satsujin. I'm an orphan… and someone who died only to be reborn into a world filled with fictional stories I once knew.”I expected a cheat ability—something powerful or overpowered. But all I got… was an intense exercise method called Herculess Method and a challenging life.Now, I'm just trying to survive and stay on track.That was the plan—until I enrolled in Shuchiin Academy.And suddenly, I found myself surrounded by girls from anime I used to watch.One by one, they started getting involved with me.

In a land ruled by vile monsters, where death is common and life is cruel, one outcast endeavors to have it all. When misfortune drags the odd goblin Stryg from his forest home and into the ruthless city of Hollow Shade, he must try and adapt to a world that only sees him as a dimwit savage.Stryg finds himself embroiled in a school of magic, where an aristocrat's smile is filled with deceit and the simplest of remarks may lead to death threats. Yet nothing will stop him from aspiring to his beliefs of glory: power, honor, and food with salt.But as Stryg navigates through the muddled grey waters of the Ebon Realm, he will learn that some monsters lurk everywhere.

Yuki, a high school junior, dies heroically saving a stranger and is reincarnated in a fantasy world, where he discovers an extraordinary and unrivaled power.