Yen is held in the Wallet. Each wallet can hold a finite amount of yen, and in some cases that amount will be too low to buy certain items, limiting on a Player's purchasing abilities. For example, certain items cost over 1 million yen, and since the first wallet cannot carry that much, those items are unobtainable at that point in the game.
Players must discard Pins to receive yen. "Yen pins," are a group of pins used largely for this purpose. These pins have no use inside battle, and can be used for Tin Pin, shop quests, or Reaper wall requirements, but are mainly discarded for the amount of money denoted by their name. For example, a "10,000 Yen" pin can be discarded to put ¥10,000 into the wallet.
Yen pins are usually gained from being dropped in battle from Noise. While Yen pins can be evolved, these pins though are usually fully mastered, so cannot be mastered. Yen pins that are traded with items from the shops are not mastered, so they can be equipped in battle to make them evolve. Yen pins gain PP the same way normal combat pins gain PP, and evolve in the same manner. The pins can evolve from BPP, MPP, or SDPP. Each of these give the pin the potential to change and become a pin that is worth more. Some shop quests require specific yen pins; certain items, Books, and Swag are only available in this manner.
Regular pins also have value but are varying depending on the pin. The "Lucky" pins and other special and rare pins are valued high, granting lots of yen when recycled. Reaper and angel level pins also are valued high for their high battle capability.
There is another way to obtain yen, but it is slightly more difficult and complicated to execute, thanks to the requirements. After receiving the phone menu's "Friends" and "Mingle" modes, players can set up their own "shop". This shop will show up under the friends list of any other player that they Mingle with. If a player buys something from another player's shop, then the next time that the two players Mingle, the friend who had their shop bought from will receive half the yen spent by the other player.