Miwa Yamada, also known as Mom or Okaasan, is the mother in the Yamada family. She is married to Kento Yamada and the biological mother of Yohei Yamada. After the family adopts a lost kitten named Chi, Miwa becomes Chi's caregiver, welcoming the kitten into their home. She dedicates herself to managing domestic responsibilities as a housewife, caring for both Yohei and Chi.

Miwa exhibits a gentle and nurturing personality. Her notable cooking skills contribute to Chi's respect for her, as she provides Chi's food. While generally easygoing, glimpses suggest she was more spontaneous in her youth. Miwa actively participates in family decisions, such as advocating for the entire family to accompany Kento on a work trip.

Her relationships define her character. She shares a supportive marriage with Kento, attentively cares for and guides her son Yohei, and forms a strong maternal bond with Chi, treating her as both a pet and a daughter. This bond is mutual, with Chi developing affection for Miwa alongside the family. Throughout all documented appearances, Miwa remains consistently portrayed as a stable, caring, and integral member of the Yamada family structure.