Pretty good game so far, but it definitely needs some work. I really like the sister model she's really cute and sexy in the right ways, while still being believable. The progression is perfect so far. I really like the build-up in the game and I always appreciate when a dev doesn't rush to sex. It might be a harder sell in the short term, especially in a time where these games are sold on a month to month basis, but I think it makes for a better game as a whole in the long run.
But this game needs to be better organized. The game is pretty grindy right now, but there isn't any kind of indication as to whether or not that grinding is leading somewhere. A lot of the game is just doing things over and over until something changes. I'd recommend either noting progression through storytelling or giving some sort of visual point counter to let the player know what kind of progress is being made.
The navigation system is a bit clunky at the moment and makes it tedious to find things to do. Adding the sister icon to the room list is helpful, but there are still a lot of points where nothing is going on.
Fortunately, it's still real early in the development, so this will probably be fixed going forward.