Milena is the civilian identity and present-day incarnation of Sailor Nettuno, the Sailor Guardian of the planet Neptune and the deep sea. She is introduced during the third story arc of the anime, Sailor Moon S, as one of the Outer Senshi, a group of guardians tasked with protecting the Solar System from external threats. Unlike the Inner Senshi, who were awakened by the moon cats, Milena awakened on her own, driven by prophetic dreams and a deep sense of duty. She attends Mugen Academy alongside her partner Heles, and is known throughout the series as an exceptionally talented violinist and a gifted swimmer, skills that reflect her artistic and graceful nature.

Milena’s personality is defined by elegance, sophistication, and a calm, composed exterior. She appears gentle and polite, often carrying herself with an almost noble bearing, yet there is a sharpness beneath the surface. She can become cold and ruthless when angered, and she is not one to indulge others if she feels patronized. Her dedication to her mission as a Sailor Guardian is absolute, and she approaches her role with a clear, black-and-white sense of purpose. This unwavering commitment sometimes puts her at odds with the more compassionate and forgiving approach of Sailor Moon and the Inner Senshi, as Milena is willing to make difficult sacrifices for the greater good.

Her primary motivation is the protection of the planet and the fulfillment of her duty as an Outer Guardian. She shares a deep, unwavering bond with Heles, her partner and lover. Their relationship is one of complete trust and mutual understanding, and they act as a unified pair in both battle and daily life. Milena’s motivations are also shaped by her artistic soul; she finds solace and expression in music and painting, and her dream is to become a professional violinist. This artistic sensibility does not conflict with her warrior nature but rather complements it, giving her a sense of depth and inner life.

In the story, Sailor Nettuno plays a crucial role in the Sailor Moon S arc, initially appearing as a mysterious and somewhat aloof figure. She and Heles often operate independently from the Inner Senshi, as they believe their mission is separate and more severe. Over time, they learn to cooperate with Sailor Moon and the others, though Milena remains reserved and focused. Her key relationships include her partner Heles, with whom she shares a romantic and fighting partnership; Setsuna, as a fellow Outer Guardian; and a respectful, if sometimes distant, rapport with Usagi. Her development sees her gradually opening up to the idea of teamwork and trust, while never losing her core sense of duty.

Notable abilities include water and ocean-based attacks, most famously Maremoto di Nettuno, which harnesses the power of the deep sea. She also possesses precognitive gifts, allowing her to sense danger and impending disasters, often feeling it as a disturbance in the sea. Her most important item is the Deep Aqua Mirror, a talisman that reveals the truth and can be used to expose enemies or see hidden dangers. As she grows stronger, she gains the ability to transform into Super Sailor Nettuno, an enhanced form that amplifies her powers. Throughout the series, she remains a composed, determined, and deeply capable guardian, whose elegance and ruthless dedication make her one of the most memorable figures in the Sailor Moon universe.