Megaton Nine-Tails Rush (OP07-078) - 500 Years in the Future Pre-Release Cards

[Main] If the number of DON!! cards on your field is equal to or less than the number on your opponent's field, set up to 1 of your [Foxy] cards as active.
[Trigger] Add up to 1 DON!! card from your DON!! deck and set it as active.