Or Saki: Achiga-hen/Senriyama-hen, depending on which episode are you on.
I liked the main series, Saki, which helped me get into more sports anime by being one of those shows that put equal stock in having a good time as much as winning. But mahjong, as it was then, was impenetrable to me.
When Achiga-hen came out, I was already learning Japanese mahjong. I even put the show on hold so that I could really learn the game. When I picked it up again in the middle of the Vanguards match, the results were stunning–I finally got what was happening, and not just “oh, Teru won again, and it’s a big one because everyone is stunned”. Some of the more subtle details could be picked up from Yaranakya’s excellent series of Saki posts.
My issue with the show is that it’s too short, in episode count and in adapted material. I believe if Achiga-hen appeared a year later than it came out, it would be great instead of merely good. There’s a lot to love here–I’m completely with the Achiga girls in their motivations for playing, and Senriyama’s Toki embodies the spirit of her namesake from Hokuto no Ken, fighting against immeasurable odds despite her failing body.
Because of its short length, the pacing of the show is erratic, with some matches skipped or glossed over, while others take up entire episodes. The ending of the TV series leaves a lot to be desired, as it’s just the first part of a long series of matches. Still, there’s some kind of storytelling elegance where a lot girls get characterized beyond their quirks, like Subara.
There are also cameos, and they are great.