Catherine is an Amanto, an extraterrestrial being with cat-like ears, who works as a waitress at the snack bar run by Otose in Kabukicho. She is a woman in her thirties with tanned skin, short black hair, and brown eyes. While she possesses a slender figure, her facial features are often the subject of unflattering jokes from other characters, who consider her appearance to be rough and unattractive. She typically wears a green kimono and speaks with a peculiar, halting accent that gives her dialogue a distinct rhythm, though this is later suggested to be an affectation she maintains as part of her persona.

Before her current employment, Catherine was a professional cat burglar belonging to a group of Amanto thieves called Cat's Punch. She was highly skilled in infiltration, lock-picking, and bypassing security systems, earning her a reputation in the criminal underworld. Her original plan was to infiltrate Otose's bar to rob it, but her scheme was uncovered. After being arrested and serving time, she was given a second chance by Otose, who rehired her at the snack bar. In return, Catherine made a solemn promise never to steal again, a vow she takes very seriously despite her past.

Personality-wise, Catherine is impulsive, loud, and often abrasive. She frequently yells at the members of the Yorozuya, Gintoki, Shinpachi, and Kagura, typically to demand they pay their rent or do chores around the bar. She can be selfish and exhibits a tendency to be harsh to those she considers beneath her while being meek around those stronger. However, this rough exterior masks a deep-seated loyalty and gratitude towards Otose, whom she has come to regard as a mother figure. This bond is the core of her character; she is fiercely protective of Otose and is deeply affected by any harm that comes to her. In one notable instance, she stood vigil outside Otose's hospital room for days and furiously confronted Gintoki when she believed he was unwilling to defend her.

Her role in the story is primarily that of a supporting character at Snack Otose, often serving as a source of comic relief through her arguments with the Yorozuya and her constant complaints. However, she also has moments of genuine dramatic significance. During the Kabukicho Four Devas arc, when Otose's life and life's work were threatened, Catherine broke her promise and utilized her old thieving skills to kidnap a target, proving that her abilities remained sharp and that she was willing to risk her new life for the sake of her surrogate mother.

Catherine undergoes a few key moments of development. The most significant is her romantic relationship with a man named Suemoto Suejiro. Upon falling in love, she undergoes a dramatic and comedic transformation, becoming a stunningly beautiful woman with a gentle personality. Unfortunately, this relationship ends in betrayal when Suejiro is revealed to be a marriage swindler who steals her life savings. Devastated and homeless, she is eventually comforted and brought back to work by Otose, reaffirming their mother-daughter bond and Catherine's place at the bar. As the series progresses into its final arc and beyond, Catherine is shown to have aged considerably, appearing much older than even Otose, with white hair and a more withered face, which becomes a recurring visual gag. Her notable abilities, despite her reformed status, remain her extraordinary talents as a thief, including her flexible body and unparalleled lock-picking skills, which she swears only to use in extreme circumstances for Otose's sake.