Nanashi is a black LRIG intrinsically tied to her Selector, Hanna Mikage. She originates from Hanna's repressed memories, specifically Hanna's desperate desire to remember the traumatic day her brother Yuuto died, making Nanashi a manifestation of that unresolved guilt and sorrow. Her form features long pale blonde hair, a cream-colored dress, and black tights.

She initially displays a teasing demeanor, often addressing Hanna as "Hanna-sama" and offering quips during their exchanges. This behavior, however, masks a deeply sadistic nature. Nanashi openly revels in despair, particularly Hanna's anguish upon regaining her memories. After Hanna wins all five gold coins in the Selector Battles, Nanashi fulfills her purpose by returning the repressed memory: Yuuto died in an accident at a construction site, and Hanna inadvertently led him there. Witnessing Hanna's devastation, Nanashi expresses profound satisfaction, revealing her true cruel disposition.

Following the memory restitution, Nanashi disappears into Mayu's White Room. She later reappears when summoned again as Hanna's LRIG during a subsequent round of Selector Battles. By this time, Hanna has begun to process her trauma and accept her past. Nanashi's relationship with Hanna remains functional, though her disappointment at Hanna's emotional resilience is noted, as it diminishes the despair Nanashi previously savored.

Her name, Nanashi, meaning "nameless" or "nameless one" in kanji, reflects her origin as an anonymous manifestation of buried memories. Her existence is solely defined by her role in Hanna's psychological journey, with no significant relationships beyond this dynamic.