Sasara Kusugawa holds the position of student council vice-president at Kaiyou High School, later becoming president. Initially, she displays a cold and strict demeanor, resulting in social isolation with Marianne "Maaryan" Asagiri as her only friend. The impending graduation of Marianne causes Sasara significant distress, leading her to attempt convincing Marianne to delay leaving due to fear of losing her sole companion.

Her interactions change when Takaaki Kouno volunteers to help with a student council event, marking their first meeting. After Sasara ascends to president, Takaaki becomes treasurer. Their collaborative work within the council fosters a closer relationship, catalyzing Sasara's personal growth as she gradually opens up emotionally and develops romantic feelings for Takaaki.

Sasara possesses long blonde hair, typically tied with a black headband or ribbon, featuring a middle part and wavy elements. She has blue eyes, stands 163 cm tall, with measurements of 87-57-83 cm. She commonly wears the standard school sailor uniform, miniskirt, thigh-high stockings, and a ribbon headband or hair tie.

Expanded media like "ToHeart2 AnotherDays" further explores her relationships, depicting Marianne actively trying to facilitate a romance between Sasara and Takaaki. The "AnotherDays" narrative assumes a timeline where Takaaki maintains friendly relationships with multiple heroines without prior romantic commitments, enabling Sasara's interactions and emotional journey to unfold freely. Her character development consistently focuses on overcoming her initial emotional reserve through meaningful connections, particularly her student council responsibilities and evolving bond with Takaaki.