Dokin-chan is an anthropomorphic germ from Baikinman's planet, serving as his partner in antagonism. Her orange-red germ body features a white facial section extending over her nose, green eyes, small red cheeks, a single antenna, and a long tail. She has white hands and wears pink shoes.

Her personality blends selfishness, greed, and childish demands with occasional flashes of underlying kindness. She frequently orders Baikinman to fetch items, food, or people and tends to flee when disadvantaged. Despite her secondary antagonist role, she harbors a persistent romantic fixation on Shokupanman, decorating her space with his merchandise and daydreaming about romantic scenarios. This infatuation sometimes moderates her actions, leading her to object when Baikinman threatens Shokupanman.

She has a younger sister, Kokin-chan, sharing a sibling dynamic marked by both camaraderie and rivalry, especially over their mutual affection for Shokupanman. Early in the series, she wielded a specialized staff that could enlarge or shrink objects depending on contact end, though its use faded. She operates a pink UFO for transportation, deploying it occasionally to detain hostages during Baikinman's schemes.

While her core traits remain consistent, some narratives explore situational aspects. A misplaced letter once led to an unintended alliance with Currypanman, showcasing temporary cooperation and subtle connections during shared adversity; this did not result in lasting behavioral or relational changes. Her interactions, like those with Mimisensei, highlight her single-minded pursuit of Shokupanman's attention, including attempts to manipulate scenarios for romantic gain.

Introduced in the 1975 picture book "Anpanman and Dokin-chan" before her animated debut, she maintains her identity as a germ-oriented antagonist driven by self-interest, revealing nuanced layers through her unrequited affection and sporadic cooperative moments.