Pipi is the last mermaid survivor of the Triton clan genocide perpetrated by the Poseidon family. She becomes Triton's companion and ally in his quest for vengeance against Poseidon. Together, they confront Poseidon's forces, including an assault on his underwater base where human slaves initially aid them; the mission fails due to a slave's betrayal. After Triton defeats a destructive monster created by Poseidon, Pipi marries him. She later lays seven eggs, which hatch after three months into two sons and five daughters. These children are named for the rainbow's colors: Blue Triton, Green Triton, Indigo Triton, Yellow Triton, Orange Triton, Red Triton, and Violet Triton.

Conflict erupts when humans capture Green Triton during a storm. Triton's subsequent actions, manipulated by Poseidon, cause tsunamis that strike Tokyo. Poseidon frames Triton for the disasters. Pipi remains uninvolved in this incident, though it impacts her family. Following Triton's death in the final battle against Poseidon, Pipi leads their children to the dying giant turtle Ganomosu. Ganomosu offers his body as sanctuary, and Pipi establishes their permanent home on what becomes Ganomosu Island.

Pipi possesses a spirited personality and is identified as one of two surviving descendants of the sunken Atlantis. Her background connects her to Greek mythological elements within the narrative.