Menchi is a small female dog who serves as a dual-purpose pet and designated emergency food supply for the secret organization Across. Her name is derived from a word meaning minced meat, reflecting her precarious position in the household. Discovered as a stray by the overzealous agent Excel, Menchi was brought home to live with Excel and her partner Hyatt, where she remains in a constant state of alertness and fear.

Despite being unable to speak aloud, Menchi possesses a very high level of intelligence and can fully understand human language. Her internal thoughts and emotional reactions are frequently displayed for the audience through on-screen text effects. Her personality is defined by a deep, instinctual will to survive. She is resourceful and quick to notice any opportunity for escape, yet her life is marked by a profound sense of resignation and unhappiness as she is perpetually viewed as a potential meal.

Menchi's primary role in the story is that of a long-suffering victim caught in the chaos of Across's operations. Her existence fuels a recurring comedic premise where Excel and Hyatt declare a state of emergency with the intent of cooking her, though they never follow through. Several episodes, particularly the tenth and nineteenth, shift focus to her perspective, exploring her past and her desperate quest for freedom. These episodes are often structured like children's stories, contrasting their dark subject matter with a whimsical tone.

Her backstory reveals a previous owner, a kind elderly man who released her into the wild out of concern for what would become of her after his death. This abandonment, intended as an act of love, left her alone and vulnerable. Later, she has brief flashes of hope, such as when the more glamorous agent Elgala joins Across and treats her like a true pet, providing baths, walks, and luxurious meals. However, this hope is quickly tempered by the realization that even Elgala regards her as nothing more than a backup food source. Even her successful escape attempts are ultimately futile, as she inevitably crosses paths with Excel again and is recaptured.

Menchi’s key relationships are defined by exploitation. With Excel, she has a dynamic of captor and captive, where Excel shows occasional affection but never fully abandons the idea of eating her. Hyatt, in contrast, is even more fixated on Menchi’s role as rations, viewing her with a colder, more utilitarian eye. These experiences have shaped her into a deeply cynical creature; when given high-quality food, she eats it slowly, believing it to be the equivalent of a last meal for a death row inmate.

Over the course of the series, Menchi demonstrates notable abilities beyond her high intelligence. She is incredibly resilient, surviving multiple life-threatening situations and globe-trotting adventures after escaping, only to be returned to her captors. Her physical capabilities also extend to the absurd, as she has been shown operating a Gatling gun. Outside of the narrative, she performs the ending theme song for the anime episodes, communicating through a series of howls that are translated for the viewer. Her endurance of constant misery has even been recognized symbolically, with an award highlighting her as a character who embodies the modern condition of being aware of catastrophe but unable to avoid it.