Femiruna holds the title of Leo Star Maiden. She is the sole daughter of a prominent millionaire in Granvania, born into immense wealth that provides numerous servants but fosters isolation due to others treating her with excessive deference. Her appearance features distinctive cat-like ears instead of human ears, a unique trait shared only with her parents. She possesses long, curled blonde hair, dark red eyes, and a small black mole under her right eye. Elegant attire is her norm, including a signature purple dress, with alternative outfits such as a pink-and-black swimsuit and a dark violet yukata decorated with floral patterns.

Initially embodying a rich-girl stereotype, Femiruna exhibits pride, selfishness, and tsundere tendencies. She frequently dismisses servants over minor infractions, like serving meals containing carrots—a vegetable she detests without ever tasting it—highlighting her lack of practical life experience and dependence on staff. Beneath this aloof exterior lies profound loneliness stemming from her parents' constant absence and a genuine, unspoken desire for normal connections. She feels frustration when people avoid her because of her wealth and secretly yearns to explore life beyond her sheltered manor.

Her character evolves through interactions with the protagonist, Itsuki. After he confronts her about unfairly firing servants, she reconsiders her actions, offering her first apology and pledging to treat staff better. Encouraged by Itsuki, she gradually embraces new experiences: overcoming her aversion to taste carrots, attempting to learn cooking despite initial failures, and venturing into commoner spaces like general stores, finding joy in simple activities such as sampling street food. She responds positively to assertiveness, often complying with firm requests, though struggles to articulate her feelings openly unless under duress or through deep emotional bonds.

Within the game's narrative, Femiruna develops romantic feelings for Itsuki. She actively seeks self-improvement to avoid burdening him and demonstrates fierce loyalty, willing to risk her life for friends despite impulsive choices. Her storyline concludes with her leaving Granvania for Itsuki's world, where she launches a successful fashion career, winning awards for designs inspired by Granvanian motifs. She later agrees to build a future with him, including the possibility of having children.

The anime adaptation presents differences: her demeanor is less haughty, and she displays rationality under pressure while panicking in crises. Her romantic feelings emerge after being trapped with Itsuki in a confined space, a deviation some interpretations attribute to Stockholm Syndrome, contrasting the game's gradual development.

Trivia notes include her intentionally ambiguous race, sharing a blood type (B) with only one other Maiden, and participating in seasonal cultural events like wearing yukatas during the Autumn Festival.