The April 2012 Comptiq tankobon ad page features an announcement that the spin-off manga of the Fate/stay night videogame story, Fate/kaleid liner Prisma Illya, will be animated:
"The long-awaited anime green light!"
Serialized in Monthly Comp Ace, from late '07 to early '09, and then continuing in a sequel series (Fate/kaleid liner Prisma Illya Zwei), Hiroyama Hiroshi's story features Illya as protagonist. The world and characters are pretty much the same as Fate/stay night, so if you've seen the anime or read the manga adaptation of that (or maybe your gate to the Fate world was Fate/zero?), you should sense some familiarity.
It's actually unclear where the anime adaptation will start since this is an ad for the final volume of the Zwei manga. The type proclaiming #5 the last volume is right next to and as big as the anime announcement, so that may be news to fans as well.
Apparently there is supposed to be a big reveal in the March 26th issue of Comp Ace—one blogger wonders if this ad has leaked it.
via Hachima Kikou