This is absolutely adorable. I really look forward to seeing you develop the story more since you more or less have the mechanics already.
Difficulty curve can feel kinda off at times (namely in that up until Misty Crystal Cave its a breeze), but the game is pretty heavy about just how much you prepare and monhun kinda does the same thing for rank changes anyways so it could very well be intentional. I don't think stamina is ever an issue unless you fail to eat breakfast, only steps were very tight for the urgent quest.
It would be nice if there was more reason to use the other traversal terrains (mud/water) e.g. if that's how you accessed monster dens - and your character/partner could be say carried by another who can traverse those terrains so you didn't just get locked into their movement capability; but this isn't a big deal.
Team AI wise, it seems fine enough, but sometimes someone gets separated enough they just start running off lost and you either have to know how to cut them off, or hope that they can handle fights on their own that slow them down enough to catch back up with them. They can be a bit heavy on usage of attack boost/debuff effects, but I guess those can stack 5 times and there's also the Status Checker gene to make them smarter about it that I haven't been able to observe enough to see how much that changes things.
The only thing I really would encourage you to revisit however is failed mission consequences. Dropping tokies is fine since its on you to bank those, but losing equipment feels weirdly punishing (especially if you just time-out - not even get defeated) w/ no recourse currently. You might as well just save scum. If instead it generated a subquest (especially if say you could share that subquest with a friend and they get your equipment returned) or you could pay Bazel/Mailmon to retrieve items it would be probably more reasonable to continue over reloading.
Anyways, keep up the good work. ^^