When you beat an opponent in Ghost Battle Mode, you get Maxi Coins. You can get multiple Maxi Coins if you fulfil certain conditions when you win.
If you win in Ghost Battle Mode...
the "Got Maxi Coins" screen will appear
While you are playing, your Maxi Coins are displayed on the attract screen of game machines connected to yours. You will also get a ranking that will appear on the attract screens of other game machines.
The Maxi Coins you have are displayed in other game machines. Your rank depends on how many Maxi Coins you possess.
If you fulfil certain conditions when you win, you will get more Maxi Coins than usual.