Grey is average height woman. She has dark colored hair in a bob cut with some hanging in the front. She wears a dress with a light color where her breasts are, and the rest of the dress is a darker color. The dress has five connected flowers on the waist with the middle flower being the largest and the ones on the side getting smaller. There are also three vertical flower above the middle flower. In addition, she sports a light-colored belt, connected to a pouch, in which she carries her grimoire, on her left side.
As a member of the Black Bull squad, she also dons the squad's signature robe. The robe is short with the Black Bull insignia on the right side. She wears it in a way that the button which holds the robe together is located on the left of her chest.
In her first transformation, she appears as an extremely large, heavy-set man with slicked back, light-colored hair, sphere earrings with links that connect to other small sphere that hang, and glowing eyes. The rest of the appearance is not shown because of it being shaded.
Grey is an extremely shy person in her true form and becomes easily embarrassed. While transformed into someone else, Grey is friendly with others and enjoys working together with her squad mates.
At the Black Bull's headquarters, Grey is sitting on a couch while Magna and Luck bicker about something. When Captain Yami returns Grey and the other members of the squad greet him. After the introduction of Asta, Grey joins her squadmates to watch Magna preform an intiation ceremony on the new member. When Asta is acknowledged and given his robe, Grey and some other members congratulate him.
During the next day's breakfast, Grey joins her squad mates for a meal. When Asta asks what Magic Knights do, Grey transforms into Asta and says that it is interesting work and that she is looking forward to working with Asta.
Months later, Grey joins her squad mates at Raque. During their time on the beach, Grey spends most of her time transforming into other people. When Yami shows up, Grey and the rest are punished by being buried in the sand. Grey then listens when Yami explains about the Seabed Temple and how they are going to get there. A week later on the night of the their departure, Grey joins the rest of her squad in encouraging Noelle to do her best. After Noelle manages to gain control over her mana, the Black Bulls enter Noelle's spell and head to the Seabed Temple. When they reach the temple, they are guided to meet Gifso.
After meeting with Gifso and learning that they will have to play a game to obtain the magic stone, the Black Bulls, except Yami, and the priests are transported to another location. Once divided they listen to Gifso explain the rules, and Grey wonders into whom she should transform. When members of the White Night Eye arrive and join in the game, Grey helps Gauche Adlai by transforming into him during his battle to distract the opponent while Gauche attacks from behind. After the battle Grey is carried to another location by Gauche when they notice a sleeping Charmy Pappitson. Grey and Gauche are suddenly trapped within a spell and confronted by an enemy. When Gauche figures out what to do and tells Grey, she transforms a rock into a large piece of meat so that Charmy will attack the member of the White Night Eye to obtain the meat. After Charmy defeats the member, Gauche notices that Grey has used to much mana and her transformation is undone, revealing that she is a woman. Grey tells them not to look because it is embarrassing for her to be seen by others. Charmy comments about how cute Grey looks and asks how old Grey is, to which she responds that she is 24.
Grey then accompanies both Charmy and Gauche to fight Vetto but they are too late as Vetto was defeated. Later Grey is in the same room and most of the Black Bulls resting. Grey tells them to not look at her since it is so embarrassing. When then temple's citizens show up to cheer for the Black Bulls, Grey expresses her desire to get over her embarrassment. The next day Grey leaves the Seabed Temple with the rest of the Black Bulls. Once back at the Black Bulls headquarters, Grey is with everyone in the common room being patted on the back while hiding her face.
A few weeks later, Grey tries to socialize with Gauche and Gordon Agrippa. However, they are interrupted when Rades Spirito, Sally, Valtos, and an army of corpses attack the Black Bulls base. When Sally tries to attack Gordon, Grey uses her new spell to transmute Sticky Salamander into Crystal Magic, allowing Gauche to destroy it. Rades then summons No.0 - Michael Caesar and easily defeats the Black Bulls, but Grey refuses to give up after reflecting on what the squad and base mean to her.
Grey is surprised when Henry appears, and admonishes Gauche when he talks over Henry. Rades attacks the Black Bulls, but Henry protects his squadmates with part of the base and thanks them while introducing himself. Grey is terrified when Henry transforms the base into a giant minotaur and displays its destructive potential. After Sally enlarges her salamander and uses its increased viscosity to pin down the base, Gauche multiplies Grey and she transmutes the gel into Plant Magic so that Gordon's magic is more effective. Taking advantage of their distraction, Rades attacks again but Henry punches the corpse, defeating it.
- Transformation Magic: Grey uses this form of magic to take the form of other human beings. She is also able to transform things other than herself, including rocks or enemy spells.
- Gauche Adlai and Grey vs. White Night Eye member: Win
- Gauche Adlai, Grey, and Charmy Pappitson vs. White Night Eye member: Win
- Gauche Adlai, Gordon Agrippa, Grey, and Henry vs. Rades Spirito and Sally: Interrupted
- Grey's favorite things are transforming and milk.
- Grey is the eighth smartest Black Bull.
- Grey ranked seventeenth in the first popularity poll.
- Grey's true appearance is teased early in the anime, as she runs behind Asta while he is wandering in Kikka.