Doctor Tofu, whose full name is Tofu Ono, is the local chiropractor running a moxibustion and acupuncture clinic in the Furinkan neighborhood. His clinic is located conveniently near the Tendo dojo, a fact that has intertwined his life with the Tendo family for a very long time. He is a tall, handsome man who presents a calm and professional demeanor, instilling confidence in his patients who generally regard him as a serious and highly knowledgeable physician. He has a particular fondness for a human skeleton model he keeps in his office, which he has affectionately named Betty. He often references Betty during his consultations in a playful manner, treating the model almost as a companion.

Underneath his professional exterior, Doctor Tofu possesses a profound and uncontrollable infatuation with Kasumi Tendo, the eldest daughter of Soun Tendo. This single personal failing overshadows all his other qualities. Whenever Kasumi is in his presence, Doctor Tofu becomes an entirely different person. His glasses fog up, his mind goes blank, and he loses all control over his actions, often becoming a danger to himself and those around him. His patients in the neighborhood know to stay away from his clinic when Kasumi is visiting, as his judgment completely fails him. Examples of this behavior include dancing through the streets with his skeleton model strapped to his back after a simple phone call with her, or eating a book instead of reading it. Kasumi, for her part, is perpetually oblivious to the effect she has on him and dismisses his bizarre antics with the same gentle air she applies to all the chaos in her household. Despite his chaotic reactions to her, there are hints, particularly in the anime, that the affection might not be entirely one-sided, with suggestions that Kasumi looks upon him favorably and may be waiting for him to make a definitive move.

In the early stages of the story, Doctor Tofu plays a significant role as an ally and mentor to the main characters. He is one of the first people to recognize the potential in the contentious relationship between Ranma Saotome and Akane Tendo, and he often subtly and skillfully pushes them toward one another. For a time, he employs both Ranmas father, Genma Saotome (in his cursed panda form), and the Chinese Amazon warrior Shampoo as assistants in his clinic. He also serves as a source of early romantic inspiration for Akane herself, who had a childhood crush on him, though he was entirely unaware of her feelings. Akane eventually sets these feelings aside, in part because of his obvious devotion to her older sister.

Doctor Tofu is not just a medical doctor; he is also remarkably knowledgeable about various martial arts techniques and the human bodys pressure points. Although he is never seen actively practicing martial arts, his skill is such that Ranma himself admits Tofu is capable of hiding his presence and could be a formidable fighter. In the anime, a brief battle shows him using his pressure-point knowledge to completely paralyze an opponent and his frogs. In the manga and anime, his expertise is crucial for identifying the nature of dangerous techniques and providing cures. For instance, he is the one who identifies the Ultimate Weakness Moxibustion technique used on Ranma and directs the family to a temple where a cure can be found. He also provides a one-time cure for the Full-Body Cats Tongue pressure point. His abilities extend to precise medical applications, such as striking a pressure point on Ranma that causes his legs to give out at a very specific, predetermined time.

Doctor Tofu is a character whose presence in the story diminishes significantly over time. He is most active and vital in the early volumes of the manga, after which he disappears following volume twelve without any explanation given within the narrative. His role in the anime adaptation is expanded somewhat, with additional storylines that include a visit from his matchmaking mother, Kin, and a few more appearances in original episodes that are not part of the manga storyline. Despite his eventual departure from the main plot, he remains a well-regarded and popular character, remembered for his brief but important contributions as a doctor, a strategist, and a man hopelessly undone by love.