Red Ruby, the haughty Mermaid Princess of the Seahorse Kingdom. She is a popular princess who is full of confidence, elegant, and loves to show off her charms. Believing she is the most wonderful among the seven Mermaid Princesses, Red Ruby is the confident and elegant princess of the Seahorse Kingdom.

Orange Amber, the Mermaid Princess of the Anemone Kingdom, is cute, full of aegyo, and a great cook. She is a bright and lovely princess who enjoys being loved by everyone. Mermaid Princess Orange Amber is a lovely princess with a charming, cute personality and excellent cooking skills.

Yellow Gold, the Mermaid Princess of the Shell Kingdom, is a man of few words, timid, and very shy. She is a princess who enjoys drawing and expresses her thoughts through her art. Mermaid Princess Yellow Gold is quiet and very shy. She finds it difficult to make friends but loves expressing her heart through drawings.

Green Leaf, the Mermaid Princess of the Ray Kingdom, is a model student who is smart and loves reading books. She is a Mermaid Princess who always achieves good results with her outstanding knowledge and confidence.

Blue Sapphire, the Mermaid Princess of the Jellyfish Kingdom, is strong and has excellent athletic nerves. She has a strong competitive spirit and a lively, brave personality from growing up among three older brothers.

Indigo Keen, the Mermaid Princess of the Deep Sea Kingdom, has a quiet and blunt personality. After her kingdom was destroyed, she stayed at White Castle; she is a mysterious princess with many secrets and a lonely side.

Purple Amethyst, the Mermaid Princess of the Starfish Kingdom, is a tomboy princess with a lively and cheerful personality. She is highly curious, loves taking on new challenges, and possesses a free-spirited charm.

A wizard from the Shadow Ocean Kingdom. Kind on the outside, but behind the scenes, he frames others with lies and schemes. He is a cunning villain who seeks to destroy the friendship of the seven Mermaid Princesses and throw the Ocean Kingdoms into chaos.

Gray is a boy like a prince with handsome looks and a gentle manner. Possessing outstanding intelligence and talent, he is a figure who arouses curiosity about his identity due to the mysterious secrets he keeps. With prince-like looks and a kind personality, Gray is a smart and talented boy. However, he hides many secrets, creating a mysterious atmosphere.

Leo Wood is a human boy who keeps the Mermaid Princesses' secrets. He is a reliable ally who is kind, loyal, and does not hesitate to face danger for his friends. Leo Wood is a human boy who shares a deep friendship with the Mermaid Princesses. He is kind, loyal, and a reliable ally who always trusts and helps his friends.