Ryoko Sakaki is a second-year student at Tōtsuki Culinary Academy residing in the Polar Star Dormitory. Her family runs the respected Sakaki koji and fermented goods shop, directly shaping her culinary focus on fermentation techniques. She maintains a dedicated workshop near the dorm for creating products like shio koji and fermented rice juice, used by dorm members. Slender in build with a large bust, Ryoko possesses fuchsia hair, originally waist-length with split bangs, later cut into a chin-length bob during her second year. Her orange eyes complement her mature demeanor. Calm, level-headed, and nurturing, Ryoko acts as a "big sister" within Polar Star, offering emotional support to residents like Yuki Yoshino and Megumi Tadokoro during stressful times. This maturity provides stability amidst more eccentric personalities. She demonstrates resilience and composure under pressure, notably passing all challenges at the rigorous Tōtsuki Friendship and Rapport Training Camp. This included preparing 50 guest meals after a full day's work during a surprise midnight assignment and creating 200 breakfast egg dishes under extreme time constraints. Her culinary strength lies in fermentation, utilizing ingredients like black koji and soy natto to create dishes such as Soy Natto Curry Rice, which impressed Autumn Election judges with its deep flavor despite a plain appearance. Though she participated in the Autumn Election preliminaries without advancing, she accepted the outcome gracefully and continued supporting peers. She shared her fermentation knowledge with Soma Yukihira, aiding his preparation of fermented Pacific saury for a competition dish. Ryoko highly values camaraderie, expressing relief when all Polar Star members survived the training camp. She maintains close bonds with residents like Megumi and Yuki, often practicing cooking together, engages in serious discussions with Shun Ibusaki, and offers guidance to newer residents such as Soma.