Momo Kawamoto is the youngest of three sisters, approximately preschool age, attending daycare. She has slightly shoulder-length pinkish-orange hair with tips curling toward her face, green eyes, and pink cheeks, often dressed in long-sleeved dresses with white collars.

She radiates a cheerful, happy-go-lucky nature, though a selfish streak surfaces occasionally. Her young age explains her innocence, yet she shows distinct empathy and care, especially for her sisters and Rei Kiriyama, whom she adores, affectionately calling him "Rei-chan." Her favorite fictional character is Bodoro, inspired by Totoro.

Momo experienced significant familial loss: her father, Seijirou Amaido, abandoned the family for another woman, and her mother died during Momo's infancy. Raised primarily by her eldest sister, Akari Kawamoto, and grandfather, Someji Kawamoto, at their traditional wagashi shop, Mikazuki-dō, she grew up in a nurturing environment despite early hardship.

Her interactions with Rei highlight her family role. Once, Rei retrieved Momo from daycare at Akari's request. Walking home, a barking dog frightened Momo, causing her to fall and sustain minor injuries. Rei comforted her and tended to her wounds, an act triggering his own emotional vulnerability about past traumas. This moment illustrated Momo's dependence and her inadvertent role in deepening Rei's emotional bonds.

Momo participates in family traditions, like lighting ceremonial fires for deceased relatives with her sisters. She often helps with household tasks, such as preparing chestnuts, and enjoys shared family meals that strengthen bonds. Her presence contributes significantly to the warm, welcoming Kawamoto household, which becomes a sanctuary for Rei.

Throughout the series, Momo symbolizes childhood innocence and resilience, embodying themes of familial love and healing amidst adversity. Her subtle development, consistent with her age, reflects growth in emotional awareness and relational bonds within her immediate family.