Emerging from a moldy, discarded rice ball, Baikinman exists as a living manifestation of germs and decay. His physical form reflects this origin: green-skinned, perpetually unkempt, bearing a skull emblem on his chest, and exuding a persistent foul odor.

His core drive is spreading germs, disease, and mischief, fueled by an intrinsic hatred for cleanliness, health, and happiness. This places Anpanman—the embodiment of these opposing ideals—as his sworn enemy and primary target. Baikinman relentlessly schemes to spoil food, spread illness, or attack Anpanman and allies, deploying germ-based weapons or orchestrating chaos.

He frequently collaborates with Dokin-chan, a fellow antagonist molded from spoiled mochi. Their partnership persists through constant bickering and mutual blame for failures, with Baikinman typically leading their plots while relying on her aid. He occasionally shields Dokin-chan from greater perils, revealing protective instincts.

Baikinman engineered Baikinman Junior, a smaller germ sidekick, assuming a parental role that blends harsh demands with sporadic responsibility and care. He directs Junior in schemes, often chastising his mistakes.

Though predominantly villainous, Baikinman exhibits complexity. He temporarily allies with Anpanman against overwhelming mutual threats, motivated by self-preservation or safeguarding Dokin-chan and Junior—not altruism. Rare flashes of kindness, loneliness, or insecurity surface but never override his antagonistic essence.

Cleanliness remains his critical weakness; soap, water, or strong cleaners inflict severe pain and physical deterioration, forcing retreat. Defeats typically culminate in him soaring away, vowing revenge—a recurring cycle underscoring his persistent yet ineffective malice.

His abilities include generating and weaponizing germs into clouds or tools, alongside technical prowess for constructing machines, vehicles, and robots. Flight, enabled by a costume-integrated jetpack or similar device, further enables his pursuits.