"10-sai Kaa-san" centers around a young boy named Shou who, after a mysterious incident, finds his mother transformed into a 10-year-old child. Despite her physical regression, she retains her adult memories, personality, and maternal instincts. The series explores the challenges and humorous situations that arise as Shou navigates daily life with his now-childlike mother, who continues to care for him despite her new appearance.

The narrative delves into the dynamics of their relationship, blending comedy with heartfelt moments. Shou struggles with the embarrassment of having a mother who looks like a classmate, while also grappling with the responsibility of protecting her secret. His mother, though physically a child, remains fiercely devoted to her son, often stepping into her parental role in unexpected ways. The story also introduces supporting characters, including Shou’s classmates and teachers, who occasionally become entangled in the peculiar circumstances surrounding his family.

Themes of family, responsibility, and identity are woven throughout the series, as Shou and his mother adapt to their unusual situation. The manga balances lighthearted humor with emotional depth, creating a unique exploration of the parent-child bond under extraordinary conditions. The interplay between Shou’s youthful perspective and his mother’s mature yet childlike presence drives the narrative, offering a fresh take on familial relationships and the challenges of growing up.