A 2006 mahjong manga by Kobayashi Ritz, serialized in Square Enix's Young Gangan, and adapted into a 2009 anime by Gonzo.
The franchise is well known for having lots of yuri subtext and girl pairings.
A spinoff, entitled Saki: Achiga-hen episode of side A, started serialization in 2011, which was adapted into an anime in 2012.
See Saki Achiga-hen wiki page.
The following tags implicate this tag: saki_achiga-hen (learn more).