Akumako is a diminutive, imp-like being, formerly imprisoned within a vase left by the deceased father of the Hokke sisters. The vessel bore a talisman and explicit instructions forbidding its opening until the youngest sister, Utano, turned eighteen. The seal was broken prematurely, however, releasing Akumako into the guardianship of the five sisters.

Upon its release, Akumako informed the Hokke sisters that their parents were combatants belonging to an evil organization. To honor their parents' unfulfilled wishes, Akumako declared the sisters must become "excellent evil" and carry on the family legacy. It acts as a guide and mentor in this attempted pursuit of villainy, revealing that each sister possesses a latent special power. When wielding their specific weapons, the sisters transform into the magical girl team Gedou Otome Tai.

Despite this objective, Akumako's designs are perpetually undermined by the sisters' inherently kind and helpful natures. Every effort to commit a malicious act inadvertently results in a positive outcome, leading the public to mistakenly perceive the group as heroes. This repeated failure to achieve true evil forms a central dynamic of its interactions.

Akumako exhibits knowledge extending beyond its immediate circumstances, including an awareness of the anime's structure, such as breaking the fourth wall to state the number of episodes remaining.

The character actively devises and commands various operations for the sisters' quest, including auditioning for voice acting roles, seeking training at the evil Jakki Corporation, invading a broadcasting station, and attempting to destroy all bathhouses. One specific tactic involved using a Kaijin Revival Crystal pendant to resurrect a deceased cicada-themed kaijin.

Akumako's fundamental nature remains ambiguous. Though introduced as a "Sealed Evil in a Can" and a self-proclaimed entity of evil, its actual alignment is debatable, given that its directives consistently result in beneficial outcomes.