Porn aside, Asagi Ryuu has this real gift for communicating a sense of the environment. The heat of the day, the cool of the evening and so on. There aren't really that many authors who do it so well, it's a shame that skill gets lost among the ever-increasing bodily fluids in his work.
Plus, he tends to be one of the more romance-oriented porn authors which certainly makes his stuff more readable.
From an artistic point of view (strictly artistic), even if his style is not something I like, his art is probably the best I've seen on this site.
- Great backgrounds, greatly detailed most of the time, helps with the next 2 points below.
- Environment is perfectly communicated (as you pointed out)
- Even atmosphere (check: http://dynasty-scans.com/chapters/i_fell_in_love_for_the_first_time_ch03#3 That moment where you can say "thats their moment, their moment alone, just for them")
- Some angled shots on the characters look GLORIOUS
- Characters posing (this comes off as weird when irl ppl aren't posing like that, but it is drawn perfectly)
- When characters are all over each other they don't like like flat images overlapping (many mangakas fail at this... so many...).
If only the porn wasn't so... porn-ish... lol.