Parasite Eve is a survival horror role-playing video game developed and published by SquareSoft (now Square Enix) for the Sony PlayStation console. The game follows the story of Aya Brea, a rookie NYPD officer who becomes embroiled in a series of bizarre and deadly events related to a genetic mutation known as mitochondria. The game combines elements of horror, science fiction, and RPG gameplay, featuring real-time battles, exploration, puzzle-solving, and character development. The game's plot is inspired by the novel of the same name by Hideaki Sena, and its gameplay mechanics were influenced by the Final Fantasy series. Parasite Eve was critically acclaimed upon its release in 1998, and is widely regarded as a classic of the survival horror genre.

Parasite Eve is a horror RPG that follows the story of NYPD rookie Aya Brea. On the night of an opera performance in Manhattan, a singer named Melissa undergoes a drastic and horrifying transformation, causing a fire that kills most of the audience. Aya, who was attending the performance, witnesses the incident and discovers that Melissa's transformation is related to a phenomenon known as mitochondria.

As the story unfolds, Aya becomes entangled in a battle against Eve, a being born from Melissa's mitochondria. Eve is determined to wipe out humanity and create a new dominant species, and Aya must stop her before it's too late. Along the way, Aya discovers the truth about her own unique physiology and her connection to the mitochondria. With the help of scientist Kunihiko Maeda and NYPD detective Daniel Dollis, Aya battles through a series of encounters with Eve and her monstrous minions in order to prevent the end of humanity.

The game is set over the course of six days, each day presenting new challenges and revelations for Aya as she battles to stop Eve's plan. As Aya progresses, she gains new powers and abilities, unlocking the potential of her own mitochondria and becoming stronger and more formidable. Ultimately, Aya must face Eve in a final showdown, with the fate of the world hanging in the balance.