Luca serves as navigator and seer aboard the space pirate vessel Bentenmaru. Her appearance features purple eyes, black hair typically tied up with two front bangs, a square eyepatch over her right eye held by strings, and a headband adorned with a purple flower and feathers. She wears a long purple dress with a belt, a purple neck collar, and a necklace holding a crystal ball. Manga adaptations depict her with dark blue-purple hair, large earphones, a dark suit with a furry collar, and a dark red-purple cloak.

Luca exhibits a reserved personality, interacting minimally with crewmates and focusing intently on her duties. Her tone rarely shifts except under significant stress. She occasionally makes cryptic statements like "I see it..." but often declines to elaborate, sometimes claiming unspoken prior warnings that irritate colleagues. Early sources indicate her crystal ball functions only as an orb-shaped monitor; she maintains the persona despite lacking actual mystical power behind her navigation.

Her background remains largely undefined, though she joined the Bentenmaru crew after former captain Ririka departed to raise her daughter Marika. During the Golden Ghost Ship arc, Luca navigated hazardous spatial conditions—harsh gravity waves and dense cosmic dust within dark nebulae and black holes—detecting a massive ring-shaped gravity source near the ghost ship's emergence point, though its nature eluded her.

In the Hakuoh Pirates arc, Luca remained undisturbed during a bio-container breach releasing virus-carrying cat-monkeys. After contracting the virus and entering quarantine, she performed a tarot reading and later used her crystal ball to correctly predict an extension of their isolation. She collaborated to create an instruction manual for operating the Bentenmaru in the crew's absence.

During the Pirate Hunter arc, Luca took a holiday. Armed men approached her, but Ririka intervened. Luca altered her plans without informing the crew. An android impersonator infiltrated the Bentenmaru to relay course data to adversaries during her absence. Upon returning, Luca delivered souvenirs and thanked crew member Kane, expressing admiration for witnessing the legendary "Blaster" (Ririka). Amid a subsequent battle, she remarked on her inability to see anything clearly.

In *Abyss of Hyperspace*, Luca cryptically foreshadowed events before the Bentenmaru rescued Kanata Mugen. After evading three military pursuers via a subspace jump, Luca reported severe route instability, warning continuation could lead to "Nirvana," and identified a nearby alternate route. The crew used it, prolonging their return to the Sea of the Morning Star. She later observed something in her crystal ball about the pursuers' identity but did not specify details.