I'm an Extra, so What? - Chapter 21: Dungeon Break

Set in a Pokéverse where the remnants of our civilization's Earth lie buried under the resurgent human/Pokémon societies, this epic Saga follows the protagonist through his journey to the heights of Pokemon Training and beyond, across a planet that was only saved from ecological disaster by an act of Arceus. As Humanity and Pokémon coexist in this fusion of settings, the story will explore themes of war, oppressive cults, and Shadow infusion, in a world where Pokémon healing and battles echo the anime in realistic, but not overtly graphic ways. Pokémon do not rip each other apart in Battles, though it can sometimes happen in the wild.This is a very long journey fic that's kind of a Crossover with everything. But with Pokémon. So you might see characters like Shaggy Rogers, or Izuku Midoriya, but with Pokémon teams. Pokémon legends like Red, Gary Oak, and the reigning World Champion, Ash Ketchum, are also, naturally, present in the setting. Think of this slice of the Pokéverse as one where it's all coming together.

The king of assassins was reborn, mastering both alchemy and poison. Sitting inside the space, there was a ghost that loved crying.

Arakawa Kouki is reincarnated to a Japan with a different history than the Japan he knows with the memories of his previous life still intact. Kouki was discouraged, “Aren’t reincarnation stories supposed to be at some fantasy world filled with swords, magic and elves?!”

A college student, accidentally reborn into the world of Naruto, becomes a member of Uchiha who is destined to be exterminated.

In this cruel ninja world, in the face of endless wars and exclusion from the village, what will Uchiha Qing do?

PS: Later in the book, the protagonist will develop a system of immortal cultivation. Cultivating Immortals in the Ninja World, have you seen it?

- Description from novelbuddy