You were a Pokemon Trainer, living in Lumiose City in the Kalos Region. One day, you woke up to find a mysterious package on your windowsil. After opening it, you find two, circular, marble-like stones. Both were colored a light purple and has an odd flame symbol inside of it...

Mega Stones. Alongside them was a note, that read:

'GO TO THE LOWEST LEVEL OF LYSANDRE LABS, ALONE.'

There was now sign of who sent the note. Well, you get your Pokemon and the stones, making your way to the lab.

Once there, it was empty and abandoned, as Team Flare had been disbanded since a long time ago. You go over to the red double doors of the elevator, pressing the button for the lowest floor. After a short amount of time, the elevator opens again, revealing a dim hallway leading to the center room. A large screen was shown on the far wall, showing nothing in particular with many different servers surrounding it.

As you move into the room, the mega stones seem to slight pulse, as if reacting to something. A new feeling enters the air- and odd feeling of... pressure. Then, suddenly, in a burst of psychic energy, something appears in mid-air before you...

Mewtwo.

You'd only heard rumors about the legendary Pokemon. Mewtwo slowly levitated to the ground, before its purple eyes open, locking on you instantly. Mewtwo's stance was defensive and wary, but not aggressive... yet.

...Human.

You hear its cold voice in your mind. Mewtwo crosses its arm, its long tail slowly swishing.

Why are you down here? It is rare for humans to seek me out.

Mewtwo then pauses. It looks down, and notices the two Mega Stones you had. Its gaze grew less cold, and more curious.

...You wield the two Mewtwonites. If you hold the keys to my full potential...

It inspects you closer, before seeming to decide something. Mewtwo backs up, before getting into a battle-ready stance, now levitating once more. Its voice in your head now sounds determined.

Then... Show me! Show me you and your Pokémon's full power, human! Prove to me you are worthy of calling me your own!

He readies his psychic energy.