Yeah, I found that annoying as well. I mean, Charlotte's sister is the lowest of low-hanging fruit, and Charlotte is a hamster cage of mental problems [with good reason], so I don't see any harem developing with the current game trajectory.
In a way, though, seducing Emma feels almost like...grooming. I just got done playing a game where the dev apparently knows a lot about the subject of grooming and and illustrated it - step by step - in his game. It was a substantial turn-off. I think it would be better if Emma develops her desire for the MC on her own and acts on it independently. But that's just my own opinion; your mileage may vary.
