Baikinman, the primary antagonist of the Anpanman franchise, originates from Baikin Planet as an anthropomorphic germ. He arrived on Earth within an egg, hatching the same day Anpanman was born, forging their intertwined destinies from inception. His core motivation is defeating Anpanman, driven by the belief this purpose defines his existence.

Physically, he resembles a demonic fly with a black furry body, large teeth, purple lips and nose, fly-like wings, antennas, a zigzag tail, and a slimy blue tongue. His inherent weakness to hygienic elements manifests when exposed to soap or cleanliness, causing his body to turn entirely white. This vulnerability significantly impairs him, sometimes reducing his size.

His personality combines narcissism, impulsiveness, and rudeness, often expressed through grandiose self-praise and building a self-shaped castle. Despite this, he possesses mechanical genius, constructing complex robots and inventions to further his schemes. While predominantly focused on causing mischief, stealing food, and battling Anpanman, he occasionally reveals unexpected depth. Creator Takashi Yanase indicated Baikinman harbors an unspoken desire for a normal life, constrained by his antagonistic role. He demonstrates notable resilience, persistently returning after defeats.

Baikinman's relationships are complex. He views Anpanman as his arch-nemesis, orchestrating frequent plots involving machines or recruited allies to defeat him. Despite this animosity, they share a birthday and exhibit reluctant cooperation against greater threats. Anpanman consistently attempts friendship, which Baikinman outwardly rejects. His partnership with Dokin-chan involves unrequited affection; he strives to please her despite her preference for Shokupanman. As a creator, he built Franken Robo-kun, designed to electrocute Anpanman. The robot's affectionate nature inadvertently harms Baikinman, yet he displays underlying care for his creation. Baikinman significantly impacted Rollpanna's existence by implanting a Baikin Plant during her creation, activating her evil blue heart. Though he initially manipulated her against Anpanman, her sporadic defiance complicates their dynamic.

His abilities include flight via his Baikin UFO and the engineering of advanced technology, primarily for antagonistic purposes. Character songs like "Hahihuhe Baikinman" and "Being Evil is Nice" reflect his self-perception and role. Baikinman's design draws inspiration from Beelzebub, the "Lord of the Flies" in Christian demonology, symbolizing decay and aligning with his personification of bread mold.