I changed this to questionable, because while it COULD be considered dirty, it doesn't actually show any nipple, and it's focusing on the kiss, even if there was nipple.
There are dirtier things than this going around as questionable, this can pass.
What I want to know is: where can I find the whole set? I've got the short series, but it seems like the set covers a bit more(maybe) than the anime did.
Search for "Sexfriend" and "HCG/H-CG" through torrents or e2dk and you'll eventually find a full pack. I've seen a complete CG set at about 30MB and another at 80MB, which puzzles me greatly since the image resolution and format are the same and it doesn't look like on has more images than the other... then again, I haven't taken a good look at either...