Oh! Oh! On Ritz's blog, it seems that the new manga with Ritz + Igarashi collaboration is another tie-in with Saki.
The story is currently unknown but will be in the same pace as the main manga (15 pages in two months?)
It's a tie-in with Achiga-hen but high speculation is that it'll star Awai. (Mainly cause Awai was the one illustrated)
http://www.sciasta.com/ritz/