Hatched from an egg arriving from Baikin Planet on the very day Anpanman was born, Baikinman’s destiny intertwined with his nemesis from the outset. His form is an anthropomorphic germ resembling a fly, featuring large teeth, light pink eyes, purple lips, antennae, wings, a zigzag tail, and a slick blue tongue. Inspired by Beelzebub, the demonic fly of Christian lore, his design embodies bread mold – the natural adversary to Anpanman's bread-based essence. Exposure to soap or cleanliness causes his body to bleach white and shrink, revealing his vulnerability to hygiene.

Personality-wise, Baikinman radiates narcissism and impulsivity, proclaiming himself a genius and residing in a castle shaped like his own head. His consuming obsession is defeating Anpanman, fueled by the conviction that this purpose defines his existence, frequently declaring, "I was born to defeat you, Anpanman!" Yet, he occasionally displays unexpected depth: a reluctant willingness to cooperate against greater threats or fleeting moments of softer emotion. Creator Yanase Takashi suggested an unspoken desire for a normal life might lie beneath his inherent role as a force of chaos.

His relationships are intricate. He views Anpanman as his arch-nemesis, sharing a paradoxical coexistence that includes rare crisis collaborations. He harbors unrequited affection for Dokin-chan, persistently aiding her schemes despite her preference for Shokupanman. As a creator, he engineered Franken Robo-kun, a robot intended to electrocute Anpanman. However, the robot's gentle nature and persistent attempts to hug Baikinman result in unintended electrocution, fostering a comedic yet poignant dynamic where Baikinman develops grudging fondness. He also significantly influenced Rollpanna's creation by implanting a "Baikin Plant," splitting her heart into red (good) and blue (evil) halves. This manipulation allows him to occasionally sway her against Anpanman, though her frequent rebellions create an unstable alliance.

Baikinman employs various inventions for his schemes, notably his personal Baikin UFO alongside other vehicles and robots. His signature catchphrase, "Hahihuheho," punctuates his mischief. Thematically, he represents unavoidable adversity, reflecting creator Yanase Takashi’s wartime experiences with suffering and resilience. Yanase emphasized Baikinman is never permanently vanquished, symbolizing life’s persistent challenges. In newer narratives, including films and spin-offs, Baikinman occasionally assumes unexpected heroic roles confronting greater threats, showcasing nuanced development beyond his antagonistic roots.