I may be a little forward here, but I think you should have a full build cycle dedicated to integrating a better quest system for more direction. Or some kind of hint system. There are numerous times I get quests or have an idea where to go, but absolutely no idea how to get there, or steps needed to start on the path for it. Some quests even seem to have me want to deal with a princess I have never even seen yet, let alone can find. A example to a previous point would be the Caveau keys. Found 2, easily. But can't get anything to find the 3rd. Im assuming I need the local princess in my party to get through a door, but so far from my experience, every princess locks you into their route to join a party. So would trying to complete that quest be worth aiming for? I have no ingame info to go off anything to know it works any different, or any hints of a direction. Also for feeding the spider side quest. How many times do I need to do it? I did it a couple then forgot about it, failing the quest. If it listed a number I would be able to focus it knowing it had an "end". Many quests suffer from ambiguity and the game seems fairly geared towards chance encounters for completing steps.
A lesser issue is it's a shame every creature isnt animated into the adult animations for the princesses combat encounters. Lots of potential visually, and would keep nice variation most of the time. Also it seems fairly hard to get adult scenes early to mid game outside of talking to strangers which is unfortunate, let alone with other princess's. Though no ideas how to make it less grindy if the players mood rises, without ruining gameplay mechanics and story. Some kind of potion you can use on Princess's when sleeping if you sneak in?