Be aware the below is breaking the game the way it is intended to be played. Only look if you don't care or had your save game erased before like me due to the patch.

1. Beat Mormo's castle.
2. At the character select screen select any character.
3. Once you wake up in the house, do not leave the house but exit to main menu instead.
4. Rinse and repeat.

- For every time you quit to main menu, you will receive an additional icon.

Enjoy and have fun!