Thank you for your feedback!
1. I'll try to do something with swimming minigame to make it easier or more obvious.
2. Stats right now used in Nami event and in mini-game after the Ash event. I already working on "upgrades" for the city where you can increase money income from work, stats income from trainings and marks from studying.
About knowing what stats to use in events, I really wanted things to develop based on your playstyle.
Perhaps I will add more detailed tips for events to the phone.
3. Invisible hidden images is really the problem, so I'll change that.
Thanks again for your feedback.
Haven't read past the first page, so please pardon me if I repeat something that someone else has said, but just a couple suggestions for you.
For the number 2, if you are having trouble deciding how much of a hint is too much of a spoiler, you could have a setting that allows the player to change to a "spoiler hints" mode that replaces the vague hints with really detailed hints. This makes it so the option is in the players' hands. If someone doesn't want too much of a spoiler they can keep the option off, but if they ever get stuck they can turn it on if they need it. And it allows the players who don't care about getting spoiled to get an easy instruction on what they need to do to get what they are looking for.
For number 3, I suggest looking into what Crimson High did with the space hamsters. He made an option to turn on a notification whenever a space hamster was on the screen. Also, Extra Life had an interesting concept of clicking on things to find money, but there was a vision mode that highlighted where the objects were for those who don't like clicking everything.