Thanks for playing! The goal is simply for both Sekibanki and Kogasa to survive to the next morning (there's a timer you can bring up on the bottom-middle of the screen). You attack the fairies away and scare humans to heal. Shrine Maidens are meant to make it hard, but their AI is currently bugged (will fix next update, hopefully).
As for why it's made in RPGMaker, I just knew how to program best in this. If I had more experience in Godot, I'd have done it in that engine instead.