I don't really like too many characters. I prefer quality over quantity. One solid character, with a good number of variation in sex scenes and overall content beats 5 characters with little individual substance and content with them. Maybe two or so, at most, but again, one solid character alone is fine.
As for the game proper, it's pretty good. I don't know if it had background music or not, sorta set in-game volume overall low, but it played not music at all for me, felt a bit dry cuz of that. The artwork is pretty good though, I've been following the artist's artworks for a year or two, and I like their style. Also, the training aspect of the different body parts was good, but would've liked some more fetish areas, like navel and mouth too, personally (Sad no blowjobs, other than the "scenes" in the ending). Also, I would've loved some more variations in the sex positions, it felt a bit static.
The game is good overall, but it's a bit pricey for the content, at 21 dollars (I did buy it, if only because I was interested in the game and have been following his progress reports for the last year or so, and he also bothered to at least have the game in English too). Still, it's selling rather well, and getting good reviews, so hopefully it motivates Dobu in the future in procusing an even more polished game.