Kei Arakawa is a second-year student at Sangamaki High School in North Osaka, and she's one of the main supporting characters in the Saki spin-off Achiga-hen episode of side-A. She's easily her school's strongest player—though that didn't stop Sangamaki from getting knocked out of the prefectural qualifiers by Senriyama High School.
The year before, Kei placed second in the national high school individual mahjong tournament, which gives you a sense of her skill level. Fans often note her status as a "monster player" for a reason: she's capable of holding her own against some seriously top-tier opponents, including both Rinkai's Satoha and Teru Miyanaga herself.
Content compiled by AnimeList.moe from publicly available sources.
