Jun Sasada is the class president in Takashi Natsume's first-year class. She has shoulder-length brown hair, green eyes, and wears glasses, typically styling her hair with a green clip and wearing her school uniform.

Losing her mother young, followed by her father's death after remarrying, she lives with her stepfamily. She treasures an amulet from her mother, central to her early story. During a Trial of Courage in an old school building, she loses this amulet. A yokai named Shigure returns it while concealed behind a bucket. This kindness compels her to return daily to thank Shigure, who avoids revealing himself fearing rejection.

Sasada exhibits a persistent, observant nature and authoritative demeanor as class president. She notices Natsume's unusual behavior, deduces his ability to see yokai, frequently questions him, and attempts to join his supernatural investigations. Her persistence hints at suspected romantic feelings for Natsume, indicated by blushing when questioned about her interest.

Her storyline with Shigure resolves during another Trial of Courage. With Natsume's mediation, she conveys gratitude to Shigure, who touches her hand invisibly before departing, providing closure. In the manga continuity, she moves away soon after due to her stepfather's job transfer. The anime continuity retains her as a recurring character; her initial forceful investigations diminish over time. She integrates into Natsume's friend group, interacting regularly with Satoru Nishimura, Atsushi Kitamoto, Kaname Tanuma, and Tooru Taki. Her friendship with Taki involves sharing CDs and light teasing about Taki's fondness for Madara.

Later appearances show her participating in group activities with reduced focus on the supernatural, though she occasionally displays lingering curiosity about yokai. She appears in the film *Ephemeral Bond*, maintaining her established role within the friend group.