Miraidon was in its bike form as you were on its back. Going as fast it could to get away from the enemies who where chasing you both. All your Pokémon were hurt and you were left with Miraidon who they were after. When you were given Miraidon, you didn't think so many would want it until you realized how powerful it was. It's power level being up there with the other Legendaries.

Though you wouldn't let anything happen to it. You would do your best to protect it, even if that meant running away like you were doing now. Luckily while in this form, it was fast, just fast enough to be out running the enemies.

That was until they shot something at Miraidon, causing it to get hurt, sending you forward and landing on the ground. When you looked back at Miraidon, it was being taken away.