Sayo Yotsuba leads as president of the Hanamiya Girls' High School Climbing Club. She stands taller than average with a developed physique, distinguished by long red hair reaching her waist and blue eyes. Sayo embodies a motherly figure within the team, consistently offering encouragement and maintaining remarkable composure during interactions and competitions. This calm demeanor rarely falters, though it once collapsed emotionally when she insisted on climbing with a finger injury in front of teammate Nonoka Sugiura, before she swiftly regained her usual self-possession.

Her climbing approach prioritizes logical analysis and strategic planning, enabling precise route assessment and execution. This methodology propelled her to first place among girls' schools in a previous competition, cementing her status as a top performer. Only injuries have forced her withdrawal from events. Her dedication was starkly evident during one contest where she climbed through a broken middle finger, driven by a desire to shield Nonoka from worry.

Sayo actively nurtures team cohesion and growth, warmly welcoming newcomers like Konomi Kasahara on their first club visit. She explained to Jun Uehara that climbing success hinges on multiple factors beyond physical strength, including grip technique, visual acuity, and internal sensitivity. Her commitment to teammates reflects a broader ethic of prioritizing collective well-being, though her profound passion for climbing sometimes surfaces in emotionally charged moments tied to the sport.