Harumi Kinoshita is the mother of the protagonist, Kazuya Kinoshita. She is a middle-aged woman with an average build, black hair styled with straight-cut bangs, and the rest of her hair is often tied up in a bun. She is relatively short compared to other female characters in the series and typically dresses in a conservative manner. She married her husband, Kazuo, when she was twenty-four years old. The couple experienced significant difficulty conceiving a child, undergoing treatment for eight years before she was finally able to give birth to their only son, Kazuya, at the age of thirty-two.

In terms of personality, Harumi is characterized as a taciturn individual who generally does not have much to say. She is often worried about how her words might affect others, particularly when speaking with Chizuru Mizuhara, and is known to apologize quickly if she fears she may have caused any undue stress or burden. Despite her quiet nature, she has expressed a desire to be a supportive person, offering herself as someone to talk to for those feeling overwhelmed by pressure.

Harumi’s role in the story is often in the background. However, she is directly involved in a significant personal conversation with Chizuru late in the series at the Hawaiians Resort. During this talk, she empathizes with Chizuru, acknowledging the heavy burden of carrying the expectations of her own mother-in-law, Nagomi Kinoshita, a feeling Harumi knows from her own experience. Harumi leads Chizuru to a display featuring a wedding gown, revealing that the resort is the very place where she and Kazuo were married. This moment provides insight into her past and her relationship with her own husband. Her key relationships are primarily with her family: her son Kazuya, her husband Kazuo, and her mother-in-law Nagomi, whose strong personality significantly influences the family dynamic. She has also held a job, having worked at the kindergarten that Kazuya attended.

Throughout the series, Harumi does not display any particular abilities, instead serving a supportive role within the family. Her development is subtle, but a late interaction with Chizuru shows her stepping out of her typical quiet demeanor to offer genuine, empathetic support and to share a deeply personal part of her history in an effort to connect with and reassure another person.