It looks like most of what I could say has been covered here already, but I'll add a few notes:
The Light Novels contain non-explicit sex "scenes" (mostly fade-outs) between a 15-year-old girl and a 16-year-old girl, and there's no sex anywhere else in the franchise (not counting fan works, of course), which is just barely below the age 16 limit. The scenes don't seem to be written with titillation as the primary goal, though; they're typically intended to be humorous.
The content in the anime and manga are pretty comparable. There are two separate things that might be of issue here:
1) The lack of pants. Fanservice without regard to age range. The only thing I have to add on this is to note the ages of some of the characters: Lucchini is the youngest, at 13. Sanya is 14, while Yoshika, Lynne, Perrine, and Eila are all 15, and the rest are 16 or older. So that's just over half the main cast who falls below the 16 limit. As noted earlier in this thread, it's a shounen series, so the age range is likely due to the characters being aged close to 15-16 (the middle of the target age range), and spread out a bit on either side.
2) Onsen scenes. All characters take part at some point, some more frequently than others, though this doesn't seem related to their age. Everything's obscured by Censor Steam
or Godiva Hair
in the broadcast versions of the episodes, while nipples are visible in the DVD versions (both in Japan and the US).
There's no question that the series features fanservice of underaged characters, but it seems to be targeted more at the young male demographic rather than at pedophiles. That being said, it could certainly attract pedophiles (particularly if everything more blatant than this is removed from the wiki, and they flock to the few exceptions left), so I'd say it's probably worth keeping an eye on the page and cleaning up any gushing about the attractiveness of any of the underaged girls.
As the nominator, I'll volunteer to keep an eye on the series page for any problems.
(If anyone's wondering why I nominated it; it's because I just knew that sooner or later someone would, so we might as well get it over with. It's a borderline case, and deserves to be discussed, at the least.)