Elfleda "Effie" Mirjasdottír, initially nicknamed Elfie, belongs to the Kýlbringa, an all-female race renowned for generating Guð Mjólk—a universal medicinal milk. Her nickname shifted to "Effie" following Princess Astarotte’s childhood mispronunciation. Appointed head maid and wet nurse at age twelve after spontaneously producing Guð Mjólk upon cradling the newborn princess, Effie dedicated her life to Astarotte’s upbringing, later overseeing the royal household’s management.

Effie possesses pink hair, emerald eyes, bovine ears and tail, and a prominent bust typical of her lineage. Her attire combines a blue maid uniform, white stockings, and a neck bell emphasizing her race’s traits. While her breast size stems partly from biological heritage, sustained growth results from gradual weight gain.

Naturally nurturing, Effie embodies maternal devotion toward Astarotte, ensuring nightly warm milk rituals and coordinating estate affairs with staff like Cú. Though composed professionally, she flusters easily, particularly around Naoya Tohara—the human consort in Astarotte’s harem. Early shyness toward him evolves into cautious acceptance as she acknowledges his sincere investment in the princess’s welfare.

Hailing from a lineage of royal wet nurses, Effie’s mother Mirja served Queen Mercelída, while sisters Edda and Est fulfill parallel roles. Kýlbringa customs dictate selecting interspecies mates solely for procreation, treating partners as genetic donors rather than family. Effie harbors unspoken affection for Naoya but suppresses her feelings pending Astarotte’s formalization of their bond, adhering to protocol and loyalty.

During Naoya’s magical incapacitation, Effie undertook intimate caregiving acts—breastfeeding and manually stimulating him—to ensure survival, balancing pragmatic resolve with personal embarrassment. This underscores her prioritization of duty over discomfort.

Narrative arcs trace her shifting dynamic with Naoya from initial wariness to reciprocal respect. While her societal role remains consistent, supplementary materials highlight enduring responsibilities and subtle emotional maturation regarding restrained romantic sentiments.