This is another one I could oogle on for ages - And no, it's not only because of the 'zomgyuri!11"-factor. I guess it's mainly the eyes again - There's something in the look both characters give off. Piercing, myserious & knowing, and uncertain, unvailing & exposed?
And well, the general layout of the thing and characters is just very... Well done and pretty. Love how it all blends together, how it so obviously shows off - but yet doesn't, and still somehow manages to give a consistent "moment on film" -feeling, despite all the pretty artsy-partsyness and show-off to it.
Oh, and what the hell happened to danbooru eating up all line feeds in the comments? =/
Yep, and in case anyone still wonders, the actual image source is a doujin named "Stem of Radiant" (http://s-o-r.net/), containing an artbook-thingy with said image and some others, as well as CD with remixed music (+ small jewel-case size individual calendar leaflet versions of the artbook images in case you got your copy from Toranoana).