Very fun, bite sized game!
Your character art is very cute and has so much personality. I especially love Wave's water themed design combining with the little pipe they have. It made me wish to see the other characters also have some kind of representation of their elemental affinity in their design as well.
The mystery mechanics are simple to understand and very well implemented. I loved the battle system in particular. Very JRPG approach to investigation! I want to see more games with that concept.
A minor nitpick about the Compare Mechanic, I was initially confused on what I need to do. At first I clicked the Compare Button to get the two note sheets to appear, so I didn't realize that I needed to click it to actually compare the note. That was definitely my fault, and should have been common sense, but I think clicking the screen to reveal the note in the first place was what confused me. Again, probably just a me thing.
You do a lot of good world building through the story, and I would love to see how it continues if you decide to. (My guess is that the Mayor is actually an evil mushroom, given the foreshadowing of the coral conversation and the parasol silhouette.)
Overall, a very fun experience!