5/5 Great Game!
There isn't a lot to say that hasn't already been said by others, but I do have a few questions / suggestions.
Firstly, are the stickers supposed to be different models than the cosplayers? And as a follow on to that, if they ARE supposed to be different (which I am hoping is the case), would it be possible to also have a gallery option similar to a pokédex style where the character models are stored as well?
Secondly, I have found a shiny - but I am wondering if there are any more? I found J at the Pikachu zone, and wondering if there is a different one waiting in the grass where Bulby resides?
Also this makes me wonder if, in future, you would be implementing shiny echoes with perhaps another pose and / or reskin? I think that would be really a great touch to an already amazing start to a game.
Finally, it would be interesting to see a redesign of the hidden story aspect. I think being able to summon them is a great idea, but also I think this should be unlocked without the hidden item. Instead the hidden quests work towards improving the skills ability, and giving them perhaps in the end another bonus effect. This way the shop upgrades could be focused more on the effectiveness or power, depending on how you would want to balance things.. Perhaps to keep it simple : each further progress with the character strengthens the power of the summon, and the shop upgrades the core of the skill? I would be interested to hear what you think :)
Keep doing what you do, this game already looks seriously well polished for being in such an early stage of development. This is one of those games where I would encourage people to seriously consider the patreon donation, because this is the kind of quality work that deserves it!
P.S. For those who are having a bad time with sticker RNG -> get a bunch of coins (10 or more) and just save your game before you spend them on the maching.. then just click the close / expand button and load up if you don't get any new stickers. I only did this for the very last sticker (Bellosum Ultra-rare), for me personally there were considerably more Braizen stickers than any other (possibly 7 or 8 Ultra-rares) and also more Pikachu stickers (3-4 Ultra-rare) before I got my Bellosum (3 Jessie Ultra-rare by the end as well). However, it did 'only' take me around 100 spooky coins to get a full book - so I think the drop rates are fair enough to not need to rely on the save exploit.