"Saki Episode of Side A" is a spin-off of the original "Saki" series, focusing on the mahjong team from Achiga Girls' Academy. The story centers on Shizuno Takakamo, a first-year student who reunites with her childhood friend, Ako Atarashi, after transferring to Achiga. Together, they revive the school's mahjong club, aiming to compete in the national high school mahjong tournament. The narrative explores their journey as they assemble a team of skilled players, including Kuro Matsumi, Yuu Matsumi, and Arata Sagimori, each bringing unique abilities and personalities to the table.

The series delves into the dynamics of the team as they train and compete in regional qualifiers, facing formidable opponents from other schools. The matches are intense, blending strategic gameplay with the characters' personal growth and camaraderie. Shizuno's leadership and Ako's determination drive the team forward, while the Matsumi sisters and Arata contribute their expertise and resolve. The story highlights the challenges of balancing individual strengths with teamwork, as well as the emotional stakes of pursuing a shared dream.

As the Achiga team progresses through the tournament, they encounter rival schools, each with their own distinct playing styles and motivations. The narrative emphasizes the psychological and tactical aspects of mahjong, showcasing how the characters adapt and overcome obstacles. Themes of friendship, perseverance, and rivalry are woven throughout, providing depth to the competitive framework. The series concludes with the team's efforts to secure a spot in the national tournament, setting the stage for further developments in the broader "Saki" universe.