Kabirunrun are small, hairy creatures capable of generating instantaneous mold growth on any surface or character they touch, with a pronounced effect on bread-based entities. They perform this action while cheerfully chanting "kabikabikabi," displaying apparent innocence and no personal malice despite their powers' destructive consequences. Their capabilities include flight and the ability to merge into larger composite forms when gathered in groups.

Functionally, they serve as thematic minions to Baikinman, aligning with his germ-based antagonism while not being of his species. This relationship positions them as persistent nuisances within the narrative. A non-canonical fan theory speculates Kabirunrun may originate from discarded, deteriorating Anpanman heads, though this remains unsubstantiated in official media. No additional background, development, or narrative evolution across official seasons, films, OVAs, or spin-offs is documented.