1. You can find them around the map (in the locations before the house gets upgraded);
2. You can add them by using a cheat code upon subscribing to Deity tier on my Patreon/SS (They won't expire unless you restart the game in a new playthrough);
3. You can win them in minigames (Very low pecentage though), you can also win them in the crane minigame;
4. You can obtain them through the Nekoya Restaurant (but if you pay yen for a fancier meal, you'll get more FPs);