Ritsuko Majima is Makoto Majima's mother. Widowed shortly after Makoto's birth, she raised him as a single mother. She runs the modest Majima Produce fruit stall in Ikebukuro, where she and Makoto sell their wares. Driven by a desire for greater financial security, Ritsuko frequently chases get-rich-quick schemes. She often presents herself as younger than her 42 years, lying about her age through her behavior and fashion choices. Her personality remains fundamentally kind and cordial, conveying warmth and approachability.

Ritsuko develops a romantic relationship with local detective Yokoyama. She also adopts Guo Shungui, a Chinese girl whose missing persons case was resolved, formalizing Guo Shungui's Japanese citizenship and integrating her into the Majima family. Ritsuko typically wears practical shop attire: a beige bandana, faded pink shirt, tan pants, navy apron, and sandals, complementing her long, tied-back light brown hair and brown eyes.

Before operating the fruit shop, she worked as a snack bar hostess. Ritsuko maintains strong community ties in Ikebukuro, exchanging gossip with neighborhood figures like Chiaki, a sex worker and Makoto's former classmate who frequents the stall. She navigates the combined demands of single parenthood, business ownership, and an unexpectedly expanded family.