Viluy serves as a member of the Witches 5, antagonists for the Death Busters during the Infinity arc. As head of the science class at Mugen Academy, her magic level registers at 202. Her primary mission utilizes advanced nano robot technology to accelerate human soul harvesting for the Death Busters. These nano bots extract souls via computer screens and can be deployed offensively to inflict gradual destruction. Viluy deploys protective barriers around herself and computerized containment barriers to trap targets, often displaying intricate chemical formulas and Periodic Table elemental abbreviations. In her civilian guise, Yui Bidou, she maintains a tall appearance with long pale hair and blue eyes. Her battle attire consists of a blue and black dress, blue tights, white boots, a blue hat, a blue wristband on her left arm, long light blue dangling earrings, and a black star necklace on a blue chain. Viluy exhibits extreme intelligence and a purely logical mindset, dismissing emotion as weakness. Functioning as Sailor Mercury's direct counterpart, Viluy specifically targets Ami Mizuno. She lures Ami into a trap at Mugen Academy using a model of the Tau Nebula, aware of Ami's secret identity. After Ami discovers the Death Busters' Daimons, Viluy activates nano robots to subdue her, attempting soul extraction via computer systems. Sailor Uranus and Sailor Neptune intervene, disconnecting the equipment. Following Ami's escape and transformation into Sailor Mercury, Viluy evades her attacks by pre-calculating their trajectories. She then traps Sailor Mercury within a computerized barrier and deploys nano robots to systematically dismantle her. The arrival of other Sailor Guardians interrupts this process; though Viluy's cybernetic shield initially protects her, she infects two bystanders with Daimon eggs, transforming them into monsters. Sailor Uranus penetrates Viluy's barrier with her Space Sword Blaster, leading to Viluy's destruction. Kaolinite later resurrects her, and Viluy participates with the other Witches 5 in an attempt to ensnare Sailor Moon. This fails when the Outer Sailor Guardians breach Mugen Academy's defenses. Viluy meets her final defeat when Sailor Neptune's Submarine Reflection attack permanently eliminates the Witches 5. Her name derives from viluite, a silicate mineral. Across adaptations, she retains her core characteristics as a technologically adept antagonist for the Death Busters, with no documented appearances beyond the Infinity arc.