Death March kara Hajimaru Isekai Kyusoukyoku (WN) - Book 15 - 15-Intermission 1: Hayato Masaki

Utsuro no Hako to Zero no Maria, or The Empty Box and The Zeroth Maria, tells the sinister story of Kazuki Hoshino, who is almost madly attached to his everyday life, and his antagonist Aya Otonashi, who suddenly transfers into his class—for the 13,118th time. She majestically announces to “break” him, without paying heed to anyone else around them.

A seemingly ordinary training exercise led Chen Jian and his squad into a completely different time and space.In the post-apocalyptic world, monsters run rampant, and the surviving humans struggle to live under their terrifying claws.To fight the monsters, the living have abandoned everything.Human nature no longer exists; beastliness is the mainstream.To defeat them, one must first become them.-----------------Chen Jian was supposed to be like the others here, pursuing the maddening evolution.But, when the tungsten-core armor-piercing round first penetrated the Kui Niu's keratin armor, he suddenly discovered...Perhaps there is another way to stay alive?

Wang Yi gets a key, opening a door in 2022 will lead to 1982, and opening a door in 1982 will return to 2022.

Two very different great eras appeared before him:

Abundant dietary protection, developed industrial products, miraculous medicines, and explosive information, this is 2022.

Simple folk customs, rich wild resources, scattered antiques, and treasures of the age, this is 1982.

Traveling between these two eras, Wang Yi didn’t think much of it, he just wanted to live a good life.

- Description from novelbuddy

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.