A special Filolial, and Filo's only disciple. She is a different species from the rest. By Motoyasu's influence, she has become a queen. Though she is highly intelligent, and capable of human speech, she acts stupid and pretends that she cannot speak human language, since she often sees Naofumi annoyed by Filo.
Piyo was raised directly under Filo and she "messed around with her for a bit". Firo fed her in excess and taught how to swim. She is slightly stronger than the rest of the normal Filolial and she can pull a cart very well, but her tends to become hungry quickly. She as well as the rest of Filo's followers say “KUE!” as opposed to "GUA!". Those that say "GUA!" are Fitoria's followers. c143
New 7 Deadly Sins c204-357
After Filo became able to fly. Naofumi told her to go abduct Piyo. So Filo brought her. Then, Piyo exposed her hostility and thanks to her pledging allegiance, turning her fury affectionate and doing a rich personal grooming, the Filolials converted to Naofumi’s camp.