Perio is an incubus practicing gynecology, running a clinic where he claims to treat women experiencing difficulties in interspecies relationships. Patients like Milfa seek solutions for anatomical incompatibilities with their partners at his clinic. He possesses the ability to create vivid sexual hallucinations, employing this power during examinations to simulate inappropriate encounters with patients without their conscious awareness. This manifested during Milfa's visit when he generated an illusion of undressing and touching her. The physical interaction was revealed as non-existent after Milfa disrupted the illusion by headbutting him.

Physically, Perio has an overly long tongue. His genitalia resemble a lamprey's, potentially facilitating energy drainage during sexual acts. A prior connection exists between Perio and Kenji, referred to as a former friendship, though specifics are undefined. Kenji reacted with urgent hostility upon learning of Milfa's visit to Perio's clinic, indicating a history of problematic behavior by Perio.

His demise occurred when Mitsuko, Kenji's grandmother, ambushed him after he fled the examination room. Mitsuko, a sorceress who sustains her youth by draining life force through sexual acts, raped Perio and absorbed his spirit, resulting in his death.