To get the Dear Sister ending over with, just grab Emily's butt in the bar scene at the beginning of the game. Bam! Done and over with.
Have to agree with
Mark Takagi on the ending scenes. To me... the massive harem orgy scenes get tedious (not just this game, but any of them I've played.) Even Treasure of Nadia, which I believe has the best graphics and smoothest animations out of any game I've played, I found myself just trying to get through the scene as fast as I could.
I would like to see more content with Sofi.... and I did discover that Sofi used to be 18 and Ada was 15 (I think) in earlier versions. My understanding is that to match with some change in the timeline they had to be made younger. But I never got a clear reason on what it was in the timeline that caused them to have to change their age. If you know more about this (or read more old posts than I did), please let me know. =)