Viluy is the witch that appears the most in the manga, making her appearance in more than 20 images! That's almost 3 times the amount of drawings Naoko ever made of Sailor Papillon! She was also given a mundane name in the mexican dub, she was called Yui Bidoo. Extremely intelligent and very snobbish, she creates a close rivalry with Amy Mizuno, especially in the anime. In the anime, she was the fourth witch to appear, and the third in the manga. VA in the Latin-American dub: Ana Marķa Grey (She also interprets Sailor Tin Nyanko and Para-Para).

She appears in the shadows a couple of times before her great debut in episode 123. In the mysterious lab of the Witches 5, she is looking at some biological samples under a microscope, possibly looking at the cellular components of the daimons before they posses something. In the episode where Mimet is playing Twister with Telu, Viluy remains quiet in a chair writing down some data.

The Sailors now have proof that the enemy is lurking in the Mugen school thanks to Telu's identity booklet. Since people from other schools can't be snooping around the building, they chose to visit the school in a day where students from all over the country are going to take some exams; and Amy, the ever clever senshi that she is, got herself enlisted in the exam so that her partners have an excuse to wander around without being bothered by anyone.

While they are inside the building, they bump into a white haired girl called Yui, who always gets tens in her exams. She makes fun of Amy's friends because she thought that smart people should only seek smart friends, not hang around with a bunch of bad students like Serena and Lita. What is even worse, she tells Amy that in the Mugen school, it's the smartest students who give the classes and not the teachers. Amy gets insulted and defends her friends saying that just because Yui is intelligent, doesn't mean she has the right to make fun of school companions.

Yui gets amused by Amy's way to defend other people and invites her to see an experiment. Since Yui is in charge of the Science department, she and her group made a miniature universe inside of a glass container. Amy is literally astonished. Yui uses the opportunity to try to invite her to join their school (and possibly become a witch herself), but Amy denies her offer, because she isn't a snob like Yui is. Yui is amused and leaves the room.

Meanwhile, Tomoe looks at all of the students hoping Viluy's plan to take their Pure heart while taking the exam will work. Yui appears before him and transforms into Viluy. Viluy, the over confident showoff that she is, shoved away Kaori to bow to Tomoe promising success. She also told him that Amy Mizuno must be a Sailor Scout.

Viluy walks around the hallways and activates her "Nanomachine", a super large computer that has absolute control over the entire school. All of the students who were applying for the exam lost their Pure Heart Crystal. Amy finds out about Yui's plan and looks for a hidden door inside of the basement, Haruka and Michiru follow her. Not only did they find Yui using her special bracelet, but they also saw the Messiah asleep.

Yui turns into Viluy and starts to attack them, at that moment the three senshi transform revealing their identities to Tomoe as well who was watching everything from a hidden camera. Viluy tries to take Sailor Mercury's Pure Heart Crystal away with a special attack, but Sailor Moon arrives on time and attacks her. The attack destroyed her bracelet which turned her own attack against her, killing her.

Viluy's manga story:

Viluy appears in the same volumes and chapters as Telu. The story is pretty much the same, but Viluy must also find Haruka and Michiru, for they have escaped from the campus (Kaori actually wanted to turn them into witch apprentices because she knew about their hidden power). Amy and friends go to the school to do the test, Viluy shows off like in the anime, and shows Amy her experiment.

But alarms everywhere go on because Haruka and Michiru got into the hideout and she attacks them. Sailor Mercury arrives and attacks her, but she is later on killed by Sailor Uranus.

Later on in manga 9, chapter 31, Kaori uses black magic to make a Viluy doll to attack Sailor Mercury with psychic attacks. Viluy tries to make Mercury hate Sailor Moon, because fighting by her side has kept her from studying to become a doctor, and Mercury actually thinks it's true. Sailor Neptune and Pluto come to the rescue using their talismans to destroy her.