There are 9 new secret cards you can find in the game. To unlock those cards you need to click on the designated area or object at least 5 times. To see the cards you collected, check your Secret Stash, it's in the Main Character's room.
Before we get started here's the cheatcode for unlocking the Secret Stash, in case you don't want to do all that clicking.
keypath99 - Unlocks all the cards in your Secret Stash. Note: To access the console for cheatcodes, click on the calendar in the Main Character's room at least 5 times.
Secret Card 100 - Beach > Food Stands:
Secret Card 101 - Main House > Jina's Room:
Secret Card 102 - Main House > Entrance:
Secret Card 103 - School > Teachers' Room:
Secret Card 104 - School > GYM:
Secret Card 105 - Lake > Lakeside:
Secret Card 106 - Mall > Cindy's Storage Room:
Secret Card 107 - Angelica's House > Living Room:
Secret Card 108 - Beach > Beach Entrance: