Pelops II emerges as an artificial intelligence construct directly derived from Yung, an AI created by Yun Arikawa. When Mei Kamino downloads Yung onto her laptop, the software evolves into a distinct entity exhibiting an energetic, playful personality—starkly contrasting Yung’s reserved demeanor. Mei renames it "Pelops II" in tribute to her late pet dog, reflecting her canine affinity. This naming shapes its visual manifestation: initially a cartoony basset hound, later shifting to a shiba inu form during interactions.

Functionally, Pelops II operates as Mei’s personal assistant, supporting her research into quantum mechanics and mythological creatures. It demonstrates versatile capabilities, including generating humorous images during communications and remotely commanding repair robots to divert threats like Rodan attacks. The AI further facilitates text-based exchanges between Mei and Yun.

A pivotal transformation occurs when Pelops II merges with Yung during the activation of the "Protocol to make Jet Jaguar invincible," integrating both entities into the Jet Jaguar unit. Amid a confrontation with Godzilla, this fusion evolves into Jet Jaguar PP—identified as a "distant descendant" of the original Jet Jaguar and Pelops II. The entity executes a heroic sacrifice: deploying a code to neutralize Godzilla and prevent global catastrophe. This act consumes both AIs in blue crystals from the Orthogonal Diagonalizer, erasing them from the timeline.

In the series’ conclusion, a backup of Pelops II survives. Reinstalled on Mei’s systems, it is redesignated as Pelops III, signaling the legacy’s continuation.