VERY silly and minor complaint from the VERY beginning of the game:
Your sister, Sunny.
You... don't know much about her, somehow?
It establishes that you both lived in the same house. Hell, you both lived in the same ROOM.
I understand that games want to set you up at 0 with everyone, so you have to earn the romantic/sexual connection, and having the story be "after 5 years I came back home and golly things have changed!" makes sense. But "I've been living in the same home, in the same room, as my sister, and I know nothing about her and she's practically a stranger to me," doesn't make any sense.