Minami Kaido, who transforms into Cure Mermaid, is a fourteen-year-old second-year student at Noble Academy where she serves as student council president. Known among her peers as the Academy Princess, she is admired for her poise, intelligence, and maturity. Minami has a calm and caring demeanor, often taking on a protective, big-sister-like role toward others. She carries a strong sense of responsibility and a desire to become a person who can be truly useful to those around her. Despite her composed exterior, she sometimes experiences loneliness, a trait that deepens her empathy for others.

As Cure Mermaid, the Princess of the Sea whose theme color is blue, Minami wields water-based abilities. She can breathe underwater and excels in aquatic combat, using high-speed maneuvers and tactics that exploit an opponent’s balance rather than relying solely on brute force. Her signature weapon is a pearl bracelet that can generate powerful waves and water attacks. She first transforms after meeting the fairies Pafu and Aroma and demonstrates an immediate aptitude for her Precure powers.

In the film Eiga Precure Dream Stars!, Minami joins her teammates Haruka Haruno (Cure Flora), Kirara Amanogawa (Cure Twinkle), and Towa Akagi (Cure Scarlet) to aid a girl named Sakura in protecting her friend Shizuku and the world of Sakuragahara. Within the Go! Princess Precure team, Minami’s calm judgment and strategic thinking complement the more impulsive energies of her companions. Her closest bonds are with Haruka and Kirara, and she shares a particularly warm friendship with Asuka Kitakaze, a recurring character from her own series.

Over the course of her journey, Minami grows from a self-reliant but somewhat isolated individual into a confident warrior who trusts her friends and opens her heart. Her dream of becoming a respectable, helpful person is realized through her role as a Precure, and her character arc emphasizes the importance of leaning on others as well as being a pillar of strength.