The supporting character's harem is very normal - Chapter 327 Why do you like me?

Lu Xiaoran has traveled to a fantasy world and received a system, but the useless system has not been activated for a long time. Lu Xiaoran, who had no choice, could only cultivate in a low-key manner and grow steadily. However, after Lu Xiaoran had become the strongest existence in the entire sect, the dog system suddenly activated.

Reborn in the world of Naruto as the Nine Tails, he finds himself sealed within Uzumaki Kushina. No longer just a mindless beast, he possesses his own will, intelligence, and the power to change the fate of the tailed beasts.Madara : I never thought that my Rinnegan would be crushed by Nine Tails.Hashirama: Times have changed. I once controlled the Nine Tails, and now the Nine Tails controls me.Uchiha Mikoto: Kushina, I didn’t expect you to have something this powerful sealed inside you.Uzumaki Kushina: Each of the Nine Tails' tails gives me a different feeling.At this moment, the Nine Tails stood tall, representing all the tailed beasts.“Tailed beasts will never be slaves!”

Yo, Hi! I’m Frank, I made a deal with a demon to pay me some money for receiving a guest for a few days every week.
I had no idea about what I have done.
On May 1st, Conan ‘the God of Death’ came to my house. I was forced to let him in and we get involved in a criminal case.
On May 8th, Bruce Wayne ‘Batman’ came to me. I was forced to follow him to fight crime.
On May 16th, Hannibal Lecter, The Silence of the Lambs, came to my home. I can only say that I really can’t stand my guests.

- Description from Novelupdates

Ye Song, who once lived in a technologically-advanced world, died and reincarnated into a noble teenager’s body in another world.

A fantasy world filled with magic!

A series of events filled with tragedy, action, etc. began to unfold one after the other when he fatefully encountered one of the most guarded secrets of this world, obtaining the legendary power of Wizards.

Watch how he reaches unreachable heights as a powerful Wizard in this new world.

- Description from Novelupdates