It's a "Tasteful panty shot" without genital exposed, no cameltoe. According to howto:rate , it should be "Safe" in DB rating, althought it's NSFW in some culture. Unless we consider this is a sexually suggestive act, I don't see how it fell out of "DB Safe".
For those who haven't yet read howto:rate, let me summarize:
Danbooru's safe/questionable/explicit rating has a specific and narrow meaning that you may not be used to, and generally a work will rate further toward the "safe" end than you may expect from the way those ratings may be used elsewhere. Now go read howto:rate.
