Kiyoko Yoshida is the kind-hearted and reliable class representative of class 2-1, a role she naturally assumes due to her caring and responsible personality. Her daily life takes an unexpected turn when Tsuyoshi Yano, a boy who arrives to class late and perpetually covered in injuries, is seated next to her. Driven by genuine concern rather than mere curiosity, Kiyoko worries that he might be the victim of bullying or domestic trouble. This concern compels her to secretly follow him home one day, at which point she discovers the surprising truth: Yano is not a victim of violence but is simply an extraordinarily clumsy and accident-prone individual.

Instead of being deterred, this revelation transforms her worry into a personal mission. Armed with a first-aid kit, Kiyoko becomes determined to care for Yano, taking it upon herself to patch up the numerous scrapes, bruises, and injuries he sustains from his daily mishaps. Her motivation is rooted in a desire to help him achieve a normal high school life, despite what seems like a cosmic streak of bad luck. At home, she finds herself constantly thinking about him, a sign of her deepening feelings that she does not immediately recognize. This leads to a period of being unknowingly in love, and it is ultimately her close friend, Mei Yuzukawa, who helps her realize that her feelings for Yano have grown beyond simple friendship or a sense of duty.

Throughout the story, Kiyoko is a dependable and expressive figure. Her dedication to Yano is persistent, and she openly declares that she will always be there to help him, a statement she recognizes sounds very much like a confession of love. Despite her reliability and emotional intelligence when it comes to caring for others, she can be prone to overthinking, especially in matters involving Yano. She also shows a sweet and affectionate side as their relationship develops, making him lunch and becoming flustered by his actions. Her caring nature is not limited to her love interest; she is also a good friend to her classmates, including Yuzukawa, Tanaka, and Yudai Hashiba, and helps care for her two younger siblings at home, further demonstrating her responsible character. She plays a key role in helping Yano overcome his personal insecurities, including showing him that his concealed right eye is beautiful, thereby building his confidence. Notably, while she excels in her class representative duties, her academic grades are surprisingly average, which adds a realistic dimension to her otherwise diligent persona.