This should make it easy!
Ah this cleared things up : http://en.wikipedia.org/wiki/Meakashi-hen
So >> Sonozaki Futago-tachi (aka Mion and Shion?) << are currently almost finished with Onikakushi-hen or the first of the four arcs of Himatsubushi-hen.
Been looking forward to seeing what the fuss is about )
Here's the demo
The easiest and cheapest way is to download the demo from this site. Don't worry about the Japanese - the download mirror sites are at the bottom of the page, so scroll down and follow the directions in English for which mirrors to use, labeled "みら〜#?. You might have to right-click and select 'save link' if it doesn't automatically begin to download the .exe file.