The Ruler Of Darkness - Chapter 17Book 5:

The strongest Demon Lord dies, and reincarnates as a human. Not only that, he because of various incidents turns into the hero’s best friend.

Follow his journey as he tries to help the hero escape his fate, and on the sideline to conquer the continent while he’s at it.

The most unlike Slytherin.

There is a saying in the Slytherin common room, “The little wizard who disobeys will be eaten by the Night Stalker.”

He is the master of the stars that shines at Hogwarts, the Night Stalker who is feared by his enemies.

The glory made him the pride of Slytherin.

When the Dark Lord arrived, he said those words,

“Weapons, I need a lot of weapons.”

With a staff in his left hand and a sword in his right hand, everyone would shout for him: “Damn the Sorting Hat, is this Slytherin?”

When the stars return to Hogwarts, John Wick’s light will shine on the entire wizarding world.

- Description from novelbuddy

An 18-year-old girl who lost her family in an accident, Yamano Mitsuha falls off a cliff one day and transferred to a different world with a civilization level of medieval Europe. Mitsuha who discovered it was possible to go and return to Earth after a deadly fight with wolves decided to live in both worlds.

「For the sake of security in old age, I will aim for 80,000 gold coins!」

I will try not to let strange things circulate and distort the progress of the world, but I won’t hold back for the sake of my easy life and safety! While carrying three handguns along with words and deeds that appear decent, in her head, Yamano Mitsuha is a sly girl.

Making an effort to make money even with a small body that looks like a child to foreigners!

Oh, my secrets are too dangerous, you said? It’s fine, it’s fine! I’ll transfer away when push comes to shove!

Zack “Kazz” Foreman once was a human from the earth when humans went through a dramatic change because of an event. This forced them to evolve into energy-based beings but was sucked into another dimension.

Forced to start living out lives on random worlds in a fractured dimension, Humanity is placed on the path of complete extinction.

This is controlled by a demon king at a place called The Center of Everything.

The Demons try to force Humanity's mark from every reality, so there are only demons, but the Demon King feeds from anger and pain. A constant tournament going at the center of everything to feed his hunger.

Kazz made it to that point once, but was tricked, refused entry to the tournament because he had offed a place one of the gods of the worlds.

Refusing to give up, Kazz goes back to the beginning to start again. To do this, Kazz must give up all of his memories to choke the flow of demons born fully grown from a pool of recycled souls.

This journey starts after he lives a solitary life trying to get stronger but not knowing why. The world Kazz is on is like our earth, but it was only a mimic of the earth we know.

Caught using steroids and about to give up and join the army, Kazz stumbles onto a cave in the ground. He is transported to a world filled with demons and monsters, and a human god named Hero is speaking in his head.

Hero, a person Kazz knew but was not friends with, followed him to help but was lost from him. Upon meeting Kazz, Hero offers him the Hero System to help him advance in this new world.

Kazz refuses after trying to get to the top and failing to use the easy route. This starts a series of frustrating events for both Heroes, but they learn to work as a team over time.

Kazz will meet misbegotten monster girls and demons that he agrees to take care of in this world, using the Ranching System. It only gives bonuses to the girls and skills to help raise them, but he will also learn to control the Elements with Shamanic abilities.