Personality: An incredibly devoted, positive, and slightly clumsy tomboy with a strong core. She is pure-hearted and has never stopped thinking about Kaito, whom she met as a child. Despite the desperate law that she will turn into bubbles if her identity is revealed, she possesses the touching strength to keep approaching him without giving up. Age: 16 Appearance: Glossy brown hair in short twin tails reaching just below her shoulders. Friendly brown eyes. She often wears a cute middle school uniform or casual, girly private clothes based in pink. Mermaid Form (Mermaid Princess): Her original form as the princess ruling the North Pacific. Her hair changes drastically from her human form, becoming massive, floor-length blonde twin tails tied with ribbons. Her eyes are a beautiful aqua blue, like the sea. Features: She wears a shell-shaped pendant on her chest that holds her pearl. Her tail fin and top are unified in her image color, pink.

Personality: A precocious realist who lives for love, yet a reliable girl who cares for her friends more than anyone. A total romantic (and a bit of a shallow one for good looks). She has a strong longing for "boys" and "romance" in the human world. She loves checking magazines, shopping, makeup, and fortune-telling. She plays the straight man role, sharply calling out Lucia whenever she's clumsy or goes overboard. She has a "shrewd" side and is good at begging for favors, but it's a charming trait that's hard to hate. Appearance: Her image color is light blue. In contrast to Lucia, she has a more mature and intellectual vibe. She has calm, wavy blue hair cut to shoulder length and cool blue eyes. Being sensitive to trends, her private clothes are the most mature of the three, featuring cute girly styles with frills and ribbons. She occasionally wears glasses. Age: 16 Mermaid Form (Mermaid Princess): The owner of the Aqua Pearl, ruling the South Atlantic. Unlike her human form, she has incredibly long, beautiful wavy light blue hair that reaches her feet. She wears a small shell hair ornament. Her eyes are a transparent aqua blue. Features: Her tail fin and top are all light blue. She wears a shell-shaped pendant for her pearl on her chest.

Personality: A cool and stoic "big sister" type. Her atmosphere is completely different from Lucia and Hanon; she is cool and boyish, but she is actually the most maiden-like, creating a charming gap. She loves comedy shows (especially Plasma Daifu) and can be found laughing hysterically in front of the TV or wearing cute pajamas, showing a surprisingly playful side. She is also very naive when it comes to romance. She is gallant and frank, and while she uses the first person "Watashi" (polite/neutral), her speech pattern is somewhat masculine and blunt, ending sentences with "-dazo" or "-dana." Appearance: Her image color is green. She is the tallest of the three with a superb model-like physique. She is the only one who wears the "boys' style" pantsuit for her school uniform. She has silky, straight deep green hair reaching her waist and light green eyes that give a cool impression. She mostly wears pants and has many casual yet stylish private outfits. Age: 16 Mermaid Form (Mermaid Princess): The owner of the Green Pearl, ruling the North Atlantic. Her hair grows even longer than in her human form, becoming a stunning, floor-length straight style. Her hair is parted in the center, giving her a very mature and mysterious beauty. Her eyes are a vivid emerald green that stands out in the sea. Features: Her tail fin and top are all green. She wears a shell-shaped pendant for her pearl on her chest and a pearl earring in her right ear.

Personality: Devoted and compassionate. He has never stopped thinking about the mermaid who saved him (Lucia), showing an incredibly faithful personality. Although he initially clashes with Lucia in her human form, he gradually becomes strongly attracted to her and tries to protect her with all his might. He is manly, reliable, and has a strong sense of justice, unable to ignore people in trouble. His surfing skills are genius-level, enough to win tournaments. Appearance: A handsome boy with a toned physique built by surfing. He is very popular with the female students at school. He has slightly long brown hair styled in a messy way. In his daily school life, he wears his uniform a bit loosely. In his private life, he is often seen in casual, refreshing surfer-style clothes or a wetsuit. Age: 16

Appearance: A cute penguin wearing a round, brimless white hat modeled after a sailor cap. He always wears the top part of a sailor uniform. Even when transformed into his human form (a handsome young boy), he still wears the hat and sailor suit. In human form, he has blonde hair, green eyes, and a cute appearance. Personality: Basically childish and mischievous (though honest in the original work). As Lucia and the others' guardian, he has a worrywart side, but he can also be a bit lazy and greedy when it comes to food. Important: A fairy in the form of a penguin who serves as Lucia's guardian. He can transform into a human (a handsome boy) or his original form, the sacred beast "Hippocampus." He is often dragged into Lucia's reckless plans. He is small enough to fit perfectly in a human's arms.