Kyōko Toshinō is a 14-year-old Nanamori Middle School student born March 28th, standing 156 cm tall with blood type B. She possesses long blonde hair usually worn down, adorned with a dark-red ribbon on top, and striking blue eyes. She is most often seen in her school uniform but favors flashy clothing and cosplay outside class, notably sporting a distinctive tomato-themed kigurumi.

Energetic, optimistic, and flamboyant, Kyōko can also be occasionally selfish. She frequently invades others' personal space without malice. Academically lazy and disliking study, she nonetheless achieves high test scores through last-minute cramming. A talented dōjinshi artist, she publishes under the pen name "Ramuko Nishikyogoku," often centering her work on the magical girl Mirakurun. Her interests include rum raisin ice cream and prioritizing otaku activities over schoolwork. This vibrant personality contrasts sharply with her timid, quiet, and easily upset childhood self.

Co-founding the Amusement Club, Kyōko maintains close bonds with its members. She frequently stays overnight at Yui Funami's apartment, recognizing Yui's unspoken loneliness. Kyōko playfully declares love for Yui, becoming agitated if Yui responds unflustered. She harbors a persistent infatuation with Chinatsu Yoshikawa due to Chinatsu's resemblance to Mirakurun, often ambushing her with hugs or teasing. Chinatsu responds with tsundere behavior, ranging from violence to moments of mutual affection like holding hands during a Christmas date.

Despite Akari Akaza being her childhood friend and the series' nominal protagonist, Kyōko unintentionally overshadows her. She teases Akari about her lack of presence and believes her hair buns are detachable. Student council vice president Ayano Sugiura secretly harbors romantic feelings for Kyōko, concealed behind a tsundere facade. Kyōko enjoys teasing Ayano, unaware of her affection, and outperforms her academically despite Ayano's diligent studying. Kyōko also bonds with Sakurako Ōmuro over similar lively personalities, engaging in activities like arcade visits.

Kyōko's empathetic side surfaces through actions like comforting lonely Yui and offering to help Ayano build closer relationships. A head injury once temporarily reverted her to her childhood personality, prompting friends to restore her usual self by hitting her head again.

In spin-offs, she appears as a supporting character in "Reset!" and features in the isekai series "Tensei Shitara Akari dake Slime datta ken."