Hot girls and great ambience. Nothing new on the porn-trope side, but the overall setting might provide some opportunity for an original story in some way.
Writing is not bad; I like the exchange between MC and "Rose" in the beginning: it's a charismatic start that, while not maintained evenly through the game, doesn't exactly fall off either. I feel like the game isn't sure whether it wants to be a standard incest porno or whether it wants to assert itself a bit more and do something more ambitious.
I really like the size and structure of the map in this game. It's an unusually interesting environment, and a great setup for puzzle elements like the locked door. If it were up to me, I'd lean into the environment by having clues distributed inconspicuously around the place and areas/characters you unlock by figuring out how to integrate those clues into answers -- a lot like the Myst games. I realize that's a very specific thing to want, but it's what occurred to me the most as I explored the map initially.
The girls could use a bit more depth as well. The author can clearly write a decent repartee; more would go a long way here. Maybe some of the characters have a backstory -- and speaking of which, why does nobody give a shit that the dad died? No need to drag it down with grief but the dude almost never comes up, which seems weird to me.
Unsolicited thoughts for the author: I'd say you have great ingredients, now focus on making it really cohesive. The music and visual environment pull the game into thoughtful, serene territory. You could have girls who take that ethos into their personalities, providing a more cerebral slow burn. The bath house can have its own story you discover slowly as you interact with it and the characters. The way you've done the art style and mapping would be a masterpiece with the right pacing and structure.
Five stars because I've never played anything that hit quite this way before and you'd be missing out if you didn't give it a try.