Because only capturing them is too easy. :V
Overdrive cards are secret spellpractice cards that can only be accessed by beating the card it was based on on all difficulties. You can see them in some way as Last Words.
Also some bonus timeouts. The first is Yuyuko's next to last card. This one gets pretty crazy if you try to time it out.
The second is a timeout of the game's final spell while bringing it to it's hardest phase as fast as possible. If there's a timeout phase I didn't notice it. Oh well.
Now stop being lazy ZUN and make an actual Overdrive difficulty mode.
