Mizushima is a supporting character in the anime Shin Atashinchi and its predecessor series. She is a middle-aged housewife in her mid-forties and a close friend of the mother of the Tachibana family. Mizushima is part of a small circle of neighborhood housewives, frequently seen alongside Toyama and the mother during their casual get-togethers, shopping trips, and conversations over tea. She is easily recognized by her triangular-shaped head and her lively, outgoing demeanor. Her personality is defined by a blend of extroversion, positivity, humility, and talkativeness. She possesses a genuinely big heart and often acts as the most socially aware member of the mothers' group, skillfully reading the atmosphere and steering conversations back on track when they become awkward or too silly. She is quick to notice if someone in the group feels uncomfortable and works to ease that tension. Mizushima enjoys gossiping, hunting for bargains, and swapping stories about the trials and humor of raising children and running a household. Her motivations are rooted in her role as a supportive friend and a dedicated homemaker. She takes pleasure in social connection and shared domestic experiences, whether that means discussing frugal shopping tips, trying out new activities like pottery classes with her friends, or simply providing a sympathetic ear. In the story, Mizushima serves primarily as a recurring foil and companion to the mother, reinforcing the series' focus on everyday social life and the dynamics of adult female friendship. Her presence highlights the mothers' shared experiences and provides a platform for comedic dialogue about marriage, parenting, and household management. Beyond her relationship with the mother, her key relationships include Toyama, another housewife in their circle, as well as her own husband and her son, Jun. Mizushima does not undergo significant dramatic development over the course of the series; she remains a consistently supportive and cheerful figure whose role is to facilitate the mother's social world and contribute to the series' slice-of-life humor. Her notable abilities include strong social intuition, a talent for de-escalating awkward situations, and an enthusiastic willingness to join in on group activities and errands. She approaches life with a humble and positive attitude, valuing the small joys of friendship and daily routines.