Midori Sawatari is a supporting character in the anime and manga series School Babysitters. She is the only infant among the children cared for at the Morinomiya Academy daycare center, and she is the daughter of Yukari Sawatari and Yutaka Sawatari. Her mother works as an office teacher at the academy, while her father is a traveling archaeologist whose profession frequently keeps him away from home on expeditions. At the beginning of the series, Midori has short, light-colored hair that gradually grows out and becomes wispier as time passes. She is the youngest and most dependent child in the daycare group and is often seen being carried by the daycare's dedicated caretaker, Yoshihito Usaida.

As an infant, Midori does not possess a developed personality in the way older characters do, but she is portrayed as a typical baby who is curious about her surroundings and responsive to the care and attention she receives. Her motivations are driven by basic infant needs such as comfort, feeding, sleep, and the desire to be held or soothed. She communicates through babbling, cooing, and simple vocalizations. A notable instance of her behavior occurs in the eleventh episode of the anime, when Usaida is unwell but still comes to the daycare; Midori shows concern by pulling at him and letting out a loud cry, demonstrating an early capacity for emotional connection and awareness of the people around her.

Midori's primary role in the story is to represent the youngest member of the daycare, highlighting the range of ages and developmental stages that the babysitters must manage. Her presence underscores the responsibility and tenderness required in childcare, especially for the most vulnerable child. She also serves as a point of connection for other characters: her mother Yukari is a colleague within the school setting, and her father's absence adds a subtle layer to the family dynamics shown in the series. The character Hiroyuki Inui, a high school student with an infatuation for Yukari, once visits the daycare specifically to see Midori, claiming she would be his future daughter.

Midori's key relationships include her bond with Usaida, who frequently holds and looks after her, and her interactions with the other daycare children, who are all slightly older and more independent. Although Midori does not undergo dramatic character development given her age, her subtle growth is evident in her physical changes, such as her lengthening hair, and in her increasing vocal responsiveness over the course of the series. Her notable ability is not a skill in the traditional sense, but rather her capacity to elicit nurturing behavior from those around her, which reinforces the central theme of care and community that defines the narrative.