(Android User) I can't find the character card thingies! It's not there!
You mean the Patreon/Subscribestar tier reward? They're on separate posts, as they're a higher tier than the game itself. You will need the base Koikatsu software to use them.
If you instead meant the heart cards (I call them that because of the heart icon)
They only appear in act 2, after you go out to the map for the first time.
