Not terribly sure why this game is rated so high. I mean it's reasonably well made, has a lot of content and keeps the quality stable but the "story" never clicked with me and all the characters felt the same.
I don't mean to bash the dev or the fans but it just popped up in the first page when sorting by rating and I can think of a lot of other games I'd put before it. Oh well.
First of all, I think a lot of us discovered it by accident and were shocked at how good it was. For whatever reason it never popped up on my radar until several months ago and then I was like DAMN HOW DID I MISS THIS???
As for why people like it, the graphics are better than >90% of the stuff on this site, and the dialogue and storytelling are mostly excellent. There are a lot of little details that work very well, like the characters making sidelong glances and brief changes in expression during dialogue that add a lot of depth to the text / story.
The LIs are overwhelmingly attractive - the game is not loaded with a bunch of fat, old, or super 'alternative' types that seem to be crowding into so many H games nowadays. The dev wisely went with hot young fit ladies for the most part, while still working in a few more niche types.
Really my only major complaint is that they started making the girls say these retarded lines like "OH YAS MAKE ME YOUR CUM SLUT UURRRGHHH" which kinda sucks but all things considered it's still a great game.