Sora Agatsuma is a left-handed power pitcher defined by her resolute declaration: "The mound is something I won't yield to anyone!" Her fastball is characterized as roaring. Her surname, Agatsuma, translates to "my wife," while her given name, Sora, means "heaven," "heavenly," "sky," or "imperial."

She joins the baseball team at Satogahama High School as a new recruit during the spring enrollment period, introduced in the OVA episode "The Story Continues" (Episode 13). This episode focuses on a new generation of players joining after the graduation of senior members. Sora arrives alongside fellow newcomers Yuzu Takanashi, Runa Kusakari, and Chiyo Sakurada. Her recruitment occurs after the events of the main television series, marking the team's continued development and expansion.