"Aggretsuko" centers on Retsuko, a 25-year-old red panda working in the accounting department of a Japanese trading company. Her daily life is marked by the monotony and frustrations of office work, including demanding bosses, tedious tasks, and workplace politics. To cope with her stress, Retsuko secretly indulges in death metal karaoke, using the aggressive music as an outlet for her pent-up emotions. This duality—her polite, reserved demeanor at work contrasted with her intense, cathartic singing—forms the core of her character.

The series explores Retsuko’s struggles with societal expectations, gender roles, and the pressures of adulthood. Her boss, Director Ton, is a chauvinistic boar who frequently belittles her, while her colleagues, such as the gossipy fennec fox Fenneko and the laid-back hyena Haida, add layers of interpersonal dynamics. Haida, in particular, harbors unspoken feelings for Retsuko, which complicates their friendship.

As the story progresses, Retsuko faces various challenges, including romantic entanglements, career aspirations, and the search for personal fulfillment. Her relationships with others, such as the ambitious washimi Gori and the carefree secretary Tsunoda, highlight different facets of her personality and the broader themes of self-discovery and resilience. The narrative often balances humor with poignant moments, reflecting the realities of modern working life.

The series also delves into Retsuko’s attempts to break free from societal norms, such as her brief foray into idol culture and her exploration of alternative career paths. These experiences underscore her desire for autonomy and happiness, even as she grapples with self-doubt and external pressures. Through its blend of workplace satire, character-driven drama, and musical interludes, "Aggretsuko" offers a relatable and multifaceted portrayal of contemporary adulthood.