Rui works as an employee at the Sansara Research Center on Kushini Island, closely associated with scientist Haruka Alford, whom she identifies as her girlfriend. She observes alarming shifts in Haruka's behavior, including intense mood swings, prolonged isolation in his lab, and uncharacteristic displays of physical strength, such as an unusually powerful handshake. These changes deeply distress her, prompting her to share her concerns with visitor Takuya Gorozu.

Driven by worry over Haruka's deteriorating mental state and physical transformation, Rui actively aids Takuya's investigation. She provides crucial assistance by enabling Takuya's unauthorized access to the Research Center's classified files. These files contain Haruka's research notes on his experiments with the "Quark of Malhuder" and his theory that an initial laser test opened a dimensional portal, allowing an entity from another dimension to enter their world. Her security breach stems directly from her concern for Haruka and desire for the truth.

Following her assistance to Takuya, Rui is confronted by Haruka and killed by him shortly after he murders an investigating soldier. Rui's death becomes a critical catalyst within the narrative; it triggers a momentary resurgence of Haruka's suppressed consciousness. Overwhelmed by his actions against Rui in this brief lucid state, he desperately contacts Takuya, pleading for him to end his life before his transformation into a vessel for the destructive entity is complete.

Rui possesses dark skin and a birthmark or mole. Her role is confined to the events depicted in the original 1987 OVA.