Confirmed: this is the cover page of Shinoasa's new doujinshi for C81. If the cover is supposed to tell us what characters we'll be seeing, I can already see tons of awesomeness coming up.
That Yuuka is particularly sweet to behold and so is Daiyousei. Seriously, Shinoasa spent so much time drawing only Mokou and Keine that his Mokou and Keine are unmatched in awesomeness, but he should try other characters more.