Erena Fujisawa is Ayano Hanesaki's childhood friend, their bond tracing back to kindergarten. She attends Kitakomachi High School, recognizable by her long black hair, brown eyes, and standard school uniform featuring a plaid skirt and ribbon tie. Smart, empathetic, and protective, Erena initially serves as the badminton club manager, actively supporting Ayano and encouraging her return to competitive play, often acting as a buffer between Ayano and others like coach Kentaro Tachibana. Despite lacking prior badminton experience, she exhibits strong will and curiosity.

When team captain Nagisa Aragaki opts out of the prefectural team tournament, Erena steps off the sidelines to become an active player. Her middle school basketball background provides athleticism, though she faces initial struggles with badminton technique. Teammates guide her, leading to gradual skill improvement. Her competitive record includes a first-round win at the Inter High Team Preliminaries followed by losses in subsequent rounds.

By her third year, Erena continues as a dedicated badminton club member while Noriko Miura assumes the manager role. Her journey evolves from a supportive figure to a participating athlete, demonstrating steadfast commitment to the team and Ayano's path. Throughout, her actions consistently focus on nurturing Ayano's reconnection with badminton and adapting to the club's demands.