Paio Zi is a six-armed demon-girl from the Magic World. A professional mercenary and bounty hunter working as part of the Canis Niger group, Paio is self-titled the The Breast Goddess and has a blatant obsession with the female form, particularly the breasts.
During a visit to the Ostianae Magnaem Thermae, the Ala Alba encounters, and is encountered by, Paio. After "sampling" the chest of Yuna Akashi, she offers Natsumi Murakami and Makie Sasaki support over their flat chests before also giving Ako Izumi a hair-growth formula after overhearing her desire to quickly grow her hair out.
Afterwards, Paio went on a groping rampage, "sampling" the chests of Kū Fei, Setsuna Sakurazaki, Nodoka Miyazaki and Konoka Konoe before being captured by Kū for being a molester, however, she was able to escape by placing the blame on Chamo.
2 years after the world of magic was revealed to the general public, Paio had moved to the Old World and had began molesting the students of Mahora Academy. After the students employed Yue Ayase to save them, Paio reveals herself and dominates Yue before being defeated and arrested by Negi Springfield who was on his way to the Ala Alba reunion.