Sasara Kusugawa is a student at Kaiyou High School, initially serving as student council vice-president before advancing to president. She stands one academic year above protagonist Takaaki Kouno. Her physical traits include long blonde hair typically parted in the middle and secured with a black headband, blue eyes, a height of 163 cm, measurements of 87-57-83 cm, and blood type AB.

Her background features a cold and strict demeanor leading to social isolation, with Marianne ("Ma-ryan") as her sole friend during their school years. Marianne's impending graduation causes Sasara significant distress, prompting attempts to dissuade her departure. After Marianne leaves, Sasara's first interaction with Takaaki occurs when he volunteers to assist the student council. Following Sasara's assumption of the presidency, Takaaki becomes treasurer. Their collaborative work fosters mutual closeness, with Sasara gradually developing romantic feelings for him.

Her personality combines a reserved, antisocial exterior with underlying shyness and nervousness, particularly in personal interactions. This contrast is evident in her evolving relationship with Takaaki, where her initial strictness softens as she becomes comfortable. Her development includes OVA appearances, such as a school festival episode illustrating her reserved nature and growing attachment to Takaaki. Later game releases added dedicated scenarios for her character. Her relationships extend beyond Takaaki, including a narrative link to the original "To Heart" series through Marianne, who shares the academic year with its characters, situating Sasara within that broader universe.