Chie Setouchi is a third-year student at Osafune Girls' Academy who wields the okatana Sohayanotsurugi. Originally from Gifu prefecture, she formed a childhood friendship with Mihono Asakura there before relocating to Okayama prefecture prior to middle school. She has attended Osafune ever since.

Chie carries herself with calm observation, preferring to assess situations from a distance. Despite this reserved approach, she often steps into others' matters, especially as an older-sister figure to Mihono. This protective dynamic includes cooking for others, though her demeanor shifts to intimidation when provoked. She enjoys knitting toys during downtime.

Physically, Chie has violet hair and blue eyes, standing 163 cm tall. Her birthday falls on February 7, and she has blood type O. A sailor uniform variant from the "Keep It Steady! Marine Style Pick-up Gacha" event serves as her alternate outfit.

She extends into the spin-off "Mini Toji," joining chibi-style depictions of daily school life alongside characters from the main series and mobile game "Toji no Miko: Kizamishi Issen no Tomoshibi."