Tomono Kojo is a first-year student in Class 1-3 at Roubai Girls' Academy, assigned seat number 6. Hailing from Nagano Prefecture, she lives with her grandmother during her studies. Her name embodies her essence: "Tomono" merges "wisdom, intellect" (智) and "from" (乃), while "Kojo" translates to "old castle, old fortress" (古城).

She possesses dark auburn hair, brown eyes, and wears glasses. Born on October 3 under the Libra sign, her quiet, gentle demeanor carries a shy edge. She immerses herself in books—essays, fantasy, mystery—with such intensity that she sometimes misses bus stops.

Her literary passion ignited in elementary school after winning first place in the 34th Literary Competition. Her mother commemorated this with a handmade pressed-flower bookmark, now her cherished good luck charm. Though she dreams of becoming an author, she grapples with finding writing topics and views reading as distinct from crafting stories.

A chance encounter with Komichi Akebi—borrowing her handkerchief to clean fogged glasses—sparked their friendship. Komichi’s vibrant spirit, like dancing in rainstorms, inspired Tomono to envision a story about her. She joined the literature club for her lifelong love of reading and the drama club, where she scripts plays for festivals, leveraging the academy’s dual-membership policy.

During school activities, she assists peers with traditional Japanese attire and competes in naginata at the sports festival. She collaborates with classmates like Touko Usagihara and Erika Kizaki, while admiring drama club president Hoko Chiarashi. On a mall trip with Komichi, Erika, Kei Tanigawa, and Touko, she lost her treasured bookmark but reclaimed it through their collective search.