OVA
Description
In the 1987 original video animation Battle Royal High School, the Fairy Master is a character named Keyn, also romanized as Kayn, who serves as a primary antagonist. She is an underling to the dark lord Byoudo, the Master of the Dark Realm, and is a key figure in his court. Her physical design is distinct and monstrous, featuring turquoise or blue skin and horns, differentiating her from any traditional or benevolent depictions of fairies. Her name is ironic, as her "fairies" are not delicate sprites but small, grotesque, bug-eyed parasites with razor-sharp teeth that infect living beings, mutating them into giant, violent monsters.

The Fairy Master is defined by her deceptive and manipulative personality. She operates as a schemer who hides her true ambitions behind a facade of loyalty. Her primary motivation is a power grab; she cannot tolerate the relentless increase of her master's power and plots to usurp him and conquer the human world for herself. Her cunning is evident when Byoudo enters the human realm to confront the martial artist Riki Hyoudo. She encourages this confrontation, feeding Byoudo a "line of garbage" because she has deduced the truth: Riki is Byoudo's human doppelganger. The Fairy Master's true scheme is to trick Byoudo into possessing Riki's body, believing that the dark lord will become vulnerable and easier to kill while limited by a human form.

Keyn's role in the story is to act as the catalyst for the conflict. She is responsible for opening the dimensional gate and releasing her parasitic fairies into the high school, mutating Riki's classmates into hideous monsters and creating widespread chaos. This directly sets the plot in motion, forcing the other main characters, such as the demon slayer Yuuki Toshihiro and the space-time officer Zankan, to intervene. Her most significant relationships are defined by betrayal. She betrays Byoudo, treating him as a pawn in her plan for conquest. She also attempts to manipulate Toshihiro to serve her purposes, even possessing his body to use him as a weapon against her enemies. Her hostile relationship with Byoudo culminates in a direct confrontation where she uses her fairy horn to transfix the combined form of Byoudo and Riki.

Throughout the OVA's single-episode runtime, the Fairy Master does not undergo a personal transformation but rather reveals her consistent nature as a treacherous opportunist. Her plan progresses from secret manipulation to open defiance. In her final battle, she taunts Byoudo about the perceived weaknesses of his human host, confident in her victory. Her defeat comes when the pain she inflicts with her fairy horn causes Riki to lose consciousness, which inadvertently removes the restrictions on Byoudo's full demonic power. He unleashes this power, ultimately killing the Fairy Master and ending her threat.

The Fairy Master possesses several notable abilities tied to her title. Her primary power is the control and deployment of her swarm of evil fairies, which she uses to possess and mutate other beings into monsters under her command. She can also take on the form of a beautiful human woman, a disguise she uses to observe the unfolding events without revealing her true nature. Additionally, she has the ability to possess others, as she does with the demon slayer Toshihiro, and wields a fairy horn as a weapon in combat.