Momo Shirosaki is a college student and the older sister of Hiro Shirosaki. She lives in the small seaside town of Hinodehama, where her grandfather runs the Kazemichi cafe that serves as a gathering place for the main characters. She has recently obtained her driver's license and drives a Daihatsu Mira Cocoa, often attaching a beginner's mark to the car in her eagerness to take friends and family for rides. In appearance, she has chest-length light brown hair and brown eyes.

Her personality is cheerful and friendly, with a playful side that shows most clearly in the way she teases her younger brother. She gave Sachi Nagamiya the nickname "Tragic Glasses Girl" and brings it up specifically to fluster Hiro, who has a crush on Sachi. Beyond these lighthearted moments, Momo is also dependable and emotionally grounded. She is devoted to her boyfriend, who is hospitalized, and visits him regularly; this relationship reveals a mature and caring side of her character.

As a supporting character, Momo provides a sibling dynamic within the story, offering a mix of comic relief and quiet support. She does not drive the main plot but interacts with the core group through family connections and casual encounters in town. Her enthusiasm for driving sometimes exceeds her skill, making her both endearing and mildly unpredictable behind the wheel. She does not possess any supernatural abilities; her role is grounded in everyday life.

Momo shows little personal development over the series—her cheerful nature and her place as a loving big sister and devoted partner remain consistent. Her key relationships are with her brother Hiro, whom she affectionately teases; her grandfather, who runs the cafe; and her hospitalized boyfriend, toward whom she demonstrates loyalty and tenderness. These connections highlight her as a warm and steady presence in the lives of those around her.