Coco is the Mermaid Princess of the South Pacific Ocean and the guardian of the yellow pearl. Her name is derived from the coconut, connecting her to her tropical domain. In terms of appearance, Coco has long, straight blond hair and yellow eyes in her mermaid form, which grows darker and shorter to shoulder length in her human guise, where her eyes also become a golden brown. Her characteristic hairstyle features short bangs that reveal her eyebrows. Among the seven princesses, she is the second oldest, with only Sara being her senior.

Coco possesses a bright, fun-loving, and caring personality. She is often cheerful and playful, and enjoys having a good time, which sometimes includes flirting with boys at the beach. However, her most defining trait is her profound loyalty to her friends, which can be so fierce that it becomes a fault. This loyalty is most powerfully demonstrated in her relationship with Sara, the princess of the Indian Ocean, who is her best friend. When Sara's heart was broken by a human, Coco tried desperately to comfort her. Witnessing her friend's spiral into despair caused Coco great personal anguish. So deep was her devotion that when Sara later threatened to destroy Coco's kingdom, Coco willingly allowed herself to be captured to appease her friend. She remained imprisoned by the sea monsters for most of the first story arc, driven by worry for Sara and a steadfast commitment to keeping her secrets.

Coco serves as a pivotal supporting character whose actions are often motivated by her protective feelings toward those she cares about. After being rescued by Lucia and the other mermaid princesses late in the first season, she plays a more active role. Having witnessed the consequences of Sara's emotional turmoil, she becomes deeply concerned about the safety of powerful artifacts like the Legendary Spiral Shell, which holds painful memories. Later, during her summer vacation in the human world with fellow princesses Noel and Caren, Coco takes on the role of a cheerful matchmaker. She concocts playful schemes to help her younger friends, such as Hanon, navigate their romantic troubles, though her efforts are not always successful and demonstrate she is not a very good actress when trying to be deceptive. Her worrying nature stems from her deep-seated loyalty and a sense of responsibility for her friends' well-being, especially after feeling powerless to help Sara.

As a mermaid princess, Coco holds the power of the yellow pearl. By using her pearl, she can transform into her idol form, known as Yellow Pearl Voice, to fend off enemies. In the anime, she uses the phrase Yellow Pearl Voice to initiate this transformation, while in the manga, she transforms simply by willing it. In this form, she wears a golden yellow dress with a high neck and a short, pleated skirt, along with pale yellow high-heeled boots and gloves. She can also assume a second, more powerful idol form, which features additional yellow-orange ruffles and a bow, similar to the other princesses. Coco's primary weapon is her singing voice, which can be used to fight enemies on its own. However, its power increases exponentially when she joins her voice in harmony with the other mermaid princesses. Notably, her emotional song is strong enough to reach Sara's heart and help set her back on the right path, even when Coco is without her pearl.