Yoshiko Igawa is the wife of Hideo Igawa and mother to Tsuyoshi, Keiko, and Noriko. She demonstrates pronounced parental favoritism, consistently showering her daughters Keiko and Noriko with greater affection and attention while frequently neglecting her son Tsuyoshi. She rarely denies requests from her daughters but assigns all household chores to Tsuyoshi, withholding similar consideration or praise.

Her interactions with Tsuyoshi involve unjustified physical and verbal abuse, including smacking and berating him, behavior never directed at her daughters. This conduct indicates increased frustration and irritability with age, contrasting sharply with descriptions of her kinder disposition in youth.

Despite her harsh treatment of Tsuyoshi, Yoshiko shares a happy and fulfilling marriage with Hideo. She exhibits occasional protectiveness towards the entire family, prepared to physically confront external threats when necessary. Her current heavier-set physique and soured countenance differ significantly from her youth; historical accounts and photographs depict her as a beautiful, dainty teenager who served on her school's cheerleading squad, closely resembling her daughter Noriko at that age. This physical change resulted from her inability to manage her eating habits over time.

Yoshiko maintains a close bond with her daughters, particularly noting Keiko's academic success and popularity. The management of her household depends entirely on Tsuyoshi's domestic capabilities, as neither she nor her daughters possess competence in cooking or cleaning.