Selena, formally known as Lunattress Andolink, holds the title of Princess of the Ocean Sprites. She bears long aqua-blue hair, wears a white dress and matching bandana, and carries the Golden Key as a necklace. Her story begins when she rescues Pinon from drowning after he tries to save the creature Papuu near the shore; she demonstrates prior knowledge of him, though the reason is unclear to Pinon at first.

A significant conflict with her mother, Seilene, drove Selena to abandon her oceanic home and live on Popolocrois's beaches. This departure inadvertently allowed the entity Zephys to possess Seilene. As a Water Sprite, Selena can transform into a radiantly beautiful, mermaid-like true form. She possesses deep kindness toward fellow Water Sprites, maintaining compassion even when Zephys corrupts them into dark sprites.

Selena's character arc centers on her relationship with Pinon, whom she has known since early childhood and harbors romantic feelings for. She sometimes exhibits jealousy toward others who show interest in Pinon, like Punpun. Her emotional resilience faces severe tests through the irreversible corruption of the dark sprites and Seilene's ultimate sacrifice to seal Zephys, events causing profound sorrow where Pinon consistently offers comfort.

Accepting her role as heir to the oceanic throne after her mother's death, Selena concludes her journey. The final scenes show her and Pinon holding hands, echoing the bond shared by his parents and symbolizing their enduring connection.