Parasite Eve is a 1998 survival horror RPG hybrid game starring Aya Brea, an NYPD officer who gets caught up in a plot that exterminate the human race. It serves as a sequel to the Parasite Eve novel. The game takes place in New York City and features a real-time battle system with random encounters. Parasite Eve received high-praise for its mature storytelling and realistic characters, unique gameplay blend, and critically-acclaimed score.
The story begins on Christmas Eve 1997, with Aya Brea, an NYPD rookie, attending an opera at Carnegie Hall with a blind date. During the opera, everyone in the building spontaneously combusts, except for Aya, and an actress on stage named Melissa Pearce.
Aya confronts Melissa onstage, as she says that Aya’s mitochondria need more time to develop. She flees backstage, with Aya giving chase. Backstage, Melissa then mutates into a beast and flees into the sewers, declaring that her name is now Eve.
The next day, on Christmas, Aya and her partner, Daniel, go to see a scientist at the Museum of Natural History named Dr. Klamp. Later that day, they hear that Eve is in Central Park, and to make matters worse, an audience has gathered at the park's theater intending to see a performance that Melissa Pearce was to give. Aya enters Central Park, but is too late to stop Eve, who causes the theater audience's mitochondria to rebel against their hosts and turns the crowd into a slimy orange mass. Aya chases after Eve and is knocked unconscious after a fight with her aboard a horse-drawn carriage. Daniel discovers that his son, Ben, was at the park, but had left the audience at the Central Park theater when he began to feel ill and when his mother began to act strange. He also learns that Manhattan is being evacuated due to the threat that Eve poses.
While Manhattan is being evacuated, a Japanese man named Kunihiko Maeda manages to sneak into the city, witnessing a police officer combust into flames in the process. The next day, Aya sees the orange mass of people from the park enter the city water supply. She goes to Dr. Klamp one more time, and discovers that Dr. Klamp has engineered special sperm for Eve so that she can create the Ultimate Being. He then spontaneously combusts. Aya finds Eve in another part of the museum, where the orange mass has surrounded her, forming an impermeable shield to protect her while the Ultimate Being gestates within her. After several failed attempts to attack Eve, the military asks Aya to attack her from a chopper, as she is the only one who can get close without combusting. The plan works, but Aya has to personally finish the fight on a now-wrecked Statue of Liberty, where Eve finally succumbs to necrosis due to her unstable cells. As Aya rests on a naval vessel, the Ultimate Being is born and attacks the surrounding ships. Aya does battle with the Ultimate Being, but its mitochondria causes it to evolve at an alarming rate. Aya sets the vessel's boiler pressure dangerously high, so as to destroy it with the Ultimate Being on board.
Parasite Eve is an action-RPG with survival horror elements. Enemies are encountered randomly whilst roaming areas, upon which the player can move Aya around to avoid enemy attacks whilst finding time to deal damage of her own. Aya can equip various firearms and can even cast spells thanks to her natural Parasite Energy abilities. Ammo and health are limited, bringing in the survival horror factor.