Demon Slayer: Worlds Collide (Kny and Pokemon Crossover Au)

When Rhea got killed by a demon, she time traveled to the future and met a boy, and they have a lot of adventures, and she discovers new creatures, and they secretly gain a crush on each other. However, when a demon time traveled there and the secret is revealed, they travel back to the Taisho era and battle the demons to maintain peace on earth.

Note: Rhea is a Kny oc who can time travel, now read the story to find out more about her