I can already tell that you're going to get a ton of comments about the combat balance from people who didn't bother to try out the elemental system. As-is the first boss makes for a good roadblock test to be sure that you've got it.
What it could use are some basics. Sound effects and music tracks are very rare and it's better to get used to the whole process of setting and changing them in RPG Maker before you get too deep into it. Even the basic set is better than silence.
The ero scenes I saw hardly had any description to go with them. The loss scene for the werewulf boss in particular had literally nothing to go on other than the pictures once it started.
All the environments feel a bit under-designed. That's something you get better at as you work with RPG Maker more, but it's worth it to be tweaking the maps you see over and over again especially so that they're not just dull grids.
Some of the skills might not be working. If "encourage" does anything then there's no visual indicator of it and Dan's guard skill doesn't seem to actually work. That one should probably be a taunt so that enemies target him - or else make his protection cover the whole party. Only guarding a single character when the targeting is random doesn't help much.
The setup runs into that isekai-specific problem where it both under-explains and over-explains itself. Like the intrigue elements (whether the goddess or the demon is lying, what his sister is doing with the demons &c) tend to work better as slow burns, but the script is in a rush to present these to you while it just kinda vibes over what the situation actually is because whatever, it's an isekai. As a result I didn't get a strong impression of any of the characters or the setting. They're all just people who show up and now you're in this place working for somebody.
You don't have to do an exposition overload, but it'd be a good idea to walk through some of the points you'd like to highlight. This is taking some obvious inspiration from games like Magical Camp and you can see what I mean by taking a look back at that. It doesn't spend a whole lot of time explaining generic elements that everybody's already familiar with, but it does have lots of details upfront to give you a sense of what the setting is like and what the situation they're facing looks like from their perspective.
Right now no one says much in camp, but you could use these NPCs to offer a sense of that. Is the situation very dire? Do you want to emphasize that their culture is very uptight, the sort that'd find the kinky demons and a hero forced to crossdress to be abominations even without all the violence? Is there some corruptive influence being felt? Giving a sense of what sort of place we're in (and whether its values feel foreign to Caelan) will go a long way toward making it feel less placeholdery.
You're on the right path with a lot of things, though. I really enjoyed what I played of it so far and look forward to seeing it progress.