Mepple flees the conquered Garden of Light as a refugee from the forces of Darkness. Arriving on Earth alongside Meppuru within a shower of shooting stars, Mepple forges an alliance with human girl Nagisa Misumi. Together, they battle the Darkness threatening both worlds. Mepple's core function is enabling Nagisa's transformation into Cure Black, one of the legendary Pretty Cure warriors. This transformative power defines Mepple's role throughout his appearances.

Mepple features consistently across the *Futari wa Pretty Cure* television series, its sequel *Futari wa Pretty Cure Max Heart*, and the related films *Futari wa Pretty Cure: Max Heart* and *Futari wa Precure Max Heart 2: Yukizura no Tomodachi*. He also appears in ensemble crossover films like *Precure All Stars DX2: Kibō no Hikari—Rainbow Jewel o Mamore!*.