Story: Basically, Higurashi Kai: Ura Higu is a bunch of 30-second shorts what are just meant to be little jokes relating to different subjects throughout the series.
Sadly, I think it failed at this. I only found about 1 or 2 out of these 24 shorts mildly funny, and they weren't brilliantly funny, just a-small-smile-on-your-face funny. I didn't really get that many of them, but I think to really find them funny you have to be into Japanese cultue and lots of general japanese things, so that could be why I didn't get their funniness.
Animation: The animation was actually pretty good, just like the original Higurashi Kai, thats about the only good point to this series though.
Sound: A few little jingles were used in this, but thats it.
Characters: Of course, as to be expected, no character development can really take place in the space of 30-seconds- nothing much really did happen at all with the characters, they just had short conversations.
Overall: Watch this is you like Higurashi and have nothing else to do with your time, but I wouldn't recommend this series. It isn't that humourous and the jokes are hard to understand.