Junko Ōsawagi is a central character in the Urayasu Tekkin Kazoku series, serving as the mother of the protagonist, Shōzō Ōsawagi, and the wife of Daitetsu Ōsawagi. Within the eccentric and chaotic Ōsawagi household, Junko functions as its anchor and de facto leader. Although she is frequently described as the most sensible member of the family and a stabilizing presence, her own personality is complex and often as extreme as those around her.

Initially portrayed as a relatively ordinary mother, Junko's character evolved significantly over the course of the series, revealing a highly capable, resourceful, and fiercely powerful individual. Her background is that of a homemaker dedicated to managing her large family. While she is proud of her family, she is constantly struggling against the chaos created by her husband, who is a heavy-smoking taxi driver with a careless attitude, and her hyperactive and trouble-making son, Shōzō. Despite the constant frustration, she is a devoted wife and a doting mother, often displaying a blind spot when it comes to her children's potential. She firmly believes that Shōzō is fundamentally a good child who can succeed when it truly matters, a conviction that often leaves others astonished.

Junko's personality is a study in contrasts. On the surface, she is a graceful and attractive woman, noted to look younger than her forty-one years, with a warm and nurturing demeanor that draws in not only her son's friends but also strangers. She is an excellent cook, a skill that her son's teacher, Harumaki, notoriously exploits under the pretense of home visits. She is also intelligent and quick-witted, capable of stepping in to teach a class when needed. However, this composed exterior hides a short-tempered and terrifyingly powerful interior. When her patience snaps, which happens frequently due to her family's antics, she transforms into a force of nature, earning her the unflattering nickname of "demon hag" from her family, who live in mortal fear of her wrath. She has a tendency to be self-righteous and can become single-mindedly focused on a task, often escalating minor situations into major incidents through her overly competent but sometimes misguided efforts.

Her role in the story is that of the ultimate problem-solver and the hidden powerhouse of the Ōsawagi family. While her son and husband are the primary instigators of the neighborhood's daily chaos, Junko is the one who ultimately restores order, often through sheer physical force. She is the undisputed strongest member of the family, and arguably one of the strongest characters in the entire series. Her husband and son are completely powerless against her; Daitetsu cannot defeat her in an arm-wrestling match without cheating, and Shōzō is known to cower simply from the low-frequency sound of her shouting voice. Her combat prowess transcends normal human limits, allowing her to single-handedly defeat the wild animals of a neighbor's house, punch a giant elementary school student known as GJG-kun into the air, and run as fast as a bus. In one notable incident, she inadvertently thwarted a bank robbery while wearing a beauty face mask and was celebrated as a hero called Iron Mama. Her signature moves include a high-angle backdrop and the People's Elbow, reflecting the series' frequent parodies of professional wrestling.

Key relationships define her position in the narrative. Her relationship with her husband, Daitetsu, is a long one, having met him when she was ten years old and he was twelve. As a child, she was an energetic and proactive girl who became fascinated by the disruptive new transfer student and persistently sought his attention until he opened up to her. As adults, she continues to manage his vices and laziness, though she inexplicably seems to have a weakness for useless men, a trait pointed out by her friends. With her son, Shōzō, she shares a bond of tough love, constantly punishing his misbehavior while remaining his most ardent fan. She is also the matriarch of the home, making most of the major decisions and ensuring the household functions, no matter how bizarre the circumstances become. Her ability to create a welcoming, if unorthodox, atmosphere makes the Ōsawagi home a regular hangout for the local children, who genuinely admire her.

Throughout the series, Junko's abilities continue to expand beyond physical strength. She has developed specialized techniques, such as the "Mature Woman Hand," a strike with a rough, winter-cracked hand capable of slicing through objects like newspaper. She has also shown proficiency in profiling, with several storylines featuring her as a psychological analyst who solves mysteries with her sharp intuition. While she is a dedicated housewife, her poor sense of direction and a peculiar fear of a doll named Aota-kun, which her youngest son brought home, stand out as some of her few weaknesses. Junko Ōsawagi is thus presented not as a mere background character, but as a formidable matriarch whose love, fury, and superhuman strength are the true glue holding her dysfunctional world together.