Yoshiko Yasukouchi is a third-year student at Shindouji Girls' High School in Fukuoka Prefecture and a supporting character in the spin-off manga "Saki: Achiga-hen episode of side-A". 

Saki's never been a big fan of mahjong. A lifetime of being forced to play with family at holidays (and losing her money as a consequence...) has left a foul taste for the game in her mouth. When she's convinced, though, to play a game with her classmates, she discovers that not only has fending off her family left her with an uncanny ability for the game but, more surprisingly, that it can even be fun!
 
Is this revelation enough to cleanse Saki's distaste for the game? Can her classmates convince her to join their club, or is there just too much baggage to make it worth her while?
 
(Source: Yen Press)

The Achiga Girls' Academy in Nara once defeated regional mahjong powerhouse Bansei High School. It advanced into the national team semifinals but lost to the eventual champion, and the mahjong club was later disbanded. 
Six years later, elementary school student Shizuno Takakamo befriends transfer student Nodoka Haramura. The two eventually enter Achiga Girls', but Nodoka transfers out of the school in the second year. 
When Shizuno sees Nodoka on television the following year as the national middle school individual mahjong champion, she decides to revive Achiga's mahjong club.

The final 4 episodes of Saki: Achiga-hen - Episode of Side-A.

The Achiga Girls' Academy in Nara once defeated regional mahjong powerhouse Bansei High School. It advanced into the national team semifinals but lost to the eventual champion, and the mahjong club was later disbanded. Six years later, elementary school student Shizuno Takakamo befriends transfer student Nodoka Haramura. The two eventually enter Achiga Girls', but Nodoka transfers out of the school in the second year. When Shizuno sees Nodoka on television the following year as the national middle school individual mahjong champion, she decides to revive Achiga's mahjong club.

Side stories of the "Saki" manga in 4-koma format. 

Note: Chapter count includes 7 omake chapters, 1 from each Volume.

Special chapters of Saki Biyori serialized in Big Gangan.