Very nice, with a little polish and find tuning the characters would look great. Not that they don't now, however as for the story, think you might be jumping the gun with the youngest sister. She is a tease, but that should not mean take me now tease as she is being pro-trade.
Its just does not feel right as each character age just feels like this game is playing with fire, but am not sure what kind game you are building. Will it be one that will keep players returning for more or one that will after you play it gets set aside and forgotten.
Currently think the per-drawn conclusion will be most will drop the older lady for the younger, which is almost main stream life.
Well good luck, i look forward to your next version. Thanks