Irukuku, also called Sylphid, is a female wind dragon serving as Tabitha's familiar. Her natural form is a blue-scaled dragon capable of flight and wind magic. She can shift into a humanoid shape resembling a tall young woman with blue hair and green eyes, visually older than Tabitha despite addressing her as "Onee-sama" (older sister). This human guise facilitates closer human interaction while preserving her draconic senses and instincts.

Tabitha rescued her from injuries, forging their lifelong familiar bond. This relationship defines her primary allegiance and motivation; her actions consistently prioritize Tabitha's safety and well-being. She accompanies Tabitha on missions, providing aerial support in combat by employing her wind magic offensively and defensively.

Her personality blends a generally sensible demeanor with bursts of childlike enthusiasm, especially concerning food or new experiences. Protective instincts drive her to intervene for Tabitha and allies during critical situations, aiding escapes or confronting threats even at personal risk. Her loyalty extends to accepting Tabitha's friends, including Saito and Louise, whom she assists in conflicts.

Her character develops through deeper integration into human social circles, particularly at Tristain Academy. Key moments include her role in rescuing Tabitha's mother, where she defies concealment protocols to provide transport, prioritizing familial bonds over secrecy. Later narrative arcs show her residing with Tabitha, Saito, Louise, and Siesta in the De Ornielle region, signifying sustained integration beyond a traditional familiar role.

While her origins predating the rescue remain unspecified, her constant presence across events—from routine academy life to large-scale battles against foes like the Ancient Dragon—underscores her enduring role as both combatant and companion within the core group's dynamics.