Switching Sides (OC x Ash x Reader)

Someone is stealing Pokémon. Ash wants to stop them and give the Pokémon back, but they are really good at their job. He knows it's not Team Rocket, but it seems they're the only ones who could've done it. At least, until he meets Melody Tyler, a girl his age with an Umbreon who can Synchro-Evolve just like him and his Greninja. She seemed like a great friend at first, with a passionate heart like his, and always wanting to helping people and Pokémon alike. She and Ash seemed like the ideal partners to solve the mystery of the missing Pokémon.

That is, until she starts acting strange. Leaving in the middle of the night, coming back hours later, and the next day another Pokémon is reported missing.

While Ash wonders about Melody, he keeps running into a peculiar someone by the name of (Y/N) at every crime scene. Ever since Melody started acting strange, she's been showing up. Suspicious, right? But that leaves Ash pondering one question... Is Melody the culprit? Or does (Y/N) have some part in the plan, too?

A/N Slight swearing and slow updates.