Character
Lucia Nanami
Lucia is Mermaid Princess of the North Pacific Ocean, keeper of the pink pearl, and the main character of the story. Lucia goes up to land to search for a boy she saved seven years ago. She is unaware of the danger in the marine world and of her real mission until she is told of them by her "older sister", Nikora.Her idol form is Pink Pearl Voice. Of all the mermaids in the series and she is junior high school student who is both blessed, and cursed, with the same personality characteristics that befall almost every shoujo heroine: a simple heart, and a simple mind. Fortunately, Lucia also has courage and determination in abundance. She lives and works in the public baths, Pearl Waters, along with her "older sister" Nikora, and her guardian penguin, Hippo.

Houshou Hanon
Hanon is Mermaid Princess of the South Atlantic Ocean and keeper of the aqua pearl. Unlike Lucia, Hanon goes up to land to escape water demons.Her idol form is Mizuiro (Aqua) Pearl Voice, although the first time that it is named in the manga, she is erroneously called Blue Pearl Voice.Hanon is also junior high school student in the same class as Lucia. In some ways, she can seem very wise and mature for someone her age, and she certainly considers herself to be quite adult-like and worldly, especially regarding her romantic pursuits. But most of the time, however, Hanon is happy to be a fun-loving, girly person. Hanon lived in an apartment by herself at the beginning of the anime, but she later moves into Pearl Waters to share a home with Lucia.

Rina Toin
Rina is Mermaid Princess of the North Atlantic Ocean and keeper of the green pearl. I nitially she is depicted as stern and bent on revenge for the capture of her best friend, Noel.Her idol form is Green Pearl Voice.Rina is also a junior high school student, in the same class as Lucia. She has a very serious, stalwart personality. She's initially somewhat of a loner, but she quickly learns to warm up to Lucia and Hanon. Because of her beauty, and her cool attitude, Rina has gained the admiration of many of the girls in her class. For some reason, she chooses to wear a boy's school uniform every day.Later, however, she evolves into a more mature character, and acts as an older sister figure to Lucia and Hanon.

Noel
Noel is Mermaid Princess of the Arctic Ocean and keeper of the deep blue (ai-iro) pearl. She helped Rina escape from the sea monsters, which led to her capture.Despite the fact that she is Caren's twin sister, Noel seems to be the polar opposite (no pun intended) of Caren in many ways. Noel has a very calm, gentle, caring personality. Rather than leaping into action, Noel instead pauses and reflects before making a decision. The only thing that Noel does impulsively, however, is jump into harm's way if that's what it takes to protect her loved ones. Noel sacrifices herself to Gakuto twice in the manga, the first time for Rina, and the second time for Caren. Noel's courage, and capacity for self-sacrifice, are the personality traits that she actually shares in common with Caren.Her idol form is Ai-iro (Deep Blue) Pearl Voice.

Caren
Mermaid Princess of the Antarctic Ocean, keeper of the purple pearl, and twin sister of Noel. In the anime, she first appears as the winner of a beauty contest that the main trio enters.Tarō asks her about his mermaid, and she later blames Rina for Noel's kidnapping. Even after things are straightened out, she chooses to go find Noel alone.She is Noel's polar opposite, having a mysterious personality. While she is cold and distant in the first season, she is found to be wild, humorous, and even a bit sexual in the second. Her idol form is Purple Pearl Voice.

Coco
Mermaid Princess of the South Pacific Ocean and keeper of the yellow pearl. She is incarcerated by the sea monsters for most of the first season, so not much is known about her. In the manga, however, she is a friend of fellow Mermaid Princess Sara. Later, she found to be playful and gentle in the manga, yet brash and outspoken in the anime.Coco still likes to have fun, hang around boys, and occassionally displays a sexy, sophisticated side of her personality.Her idol form is Yellow Pearl Voice.

Sara
Mermaid Princess of the Indian Ocean and keeper of the orange pearl. She joins Gakuto in his quest to take over the marine world after an incident bestowed her a dark power, turning both her orange hair and her orange pearl pitch black and destroying her own kingdom. That incident was a proposed rendezvous with Tarō, her secret human lover.In a fury, Sara unleashed a wave of power, destroying her kingdom and causing the wave which killed Kaito's parents and from which Lucia saved Kaito.In the manga, her villain name is Black Pearl Voice and she transforms into an idol in a black dress reminiscent of a diva. However, in the anime, she does not transform until she turns good, and instead has the power to sing offensively in a humanoid, amphibious form like the villains and mermaid idols, with or without her E-pitch. In the end, she decides to join the other mermaids as is her duty. She, herself, seals the gate to Gakto's castle in the book because it's her duty and she unsealed the gate after her kingdom was destroyed. In the TV show, Aqua Regina seals the gate and Sara goes with Gaito because she loves him. She also appears in the second season as a spirit, informing Lucia of the future Orange Pearl Voice and offering her assistance where she can. Sara is also seen singing with the other mermaid princesses in the very last episode of Mermaid Melody Pichi Pichi Pitch Pure.

Seira
Seira is introduced as the future princess of the Indian Ocean, the successor who will follow in Sara's place. However, there's just one tiny problem... Seira hasn't been born yet. Despite not yet being born, however, Seira is on some level already a self-aware entity, and she appears to Lucia as a spirit that takes the form of a young mermaid.Seira's story begins when Lucia hears a child's voice in her dreams, calling for help. Following the source of these mysterious pleas, Lucia dreams that she journeys to the ruins of the Indian Ocean kingdom. There she meets the ghost of Sara, surrounded by tiny spheres of light. Sara explains what the mysterious lights are.Unfortunately, the extraordinary energy of Seira's "fragments of the heart" are coveted by another: a villainous creature named Michel. He attacks the yet-unborn Seira, stealing the fragments of her heart. Now Lucia must pursue Michel and fight to reclaim the fragments of Seira's heart. Lucia carries the Orange Pearl with her everywhere. When she finds another fragment of Seira's heart, it is absorbed inside the Orange Pearl, and Seira learns how to feel an emotion like love, friendship, or belief in another.Once born, she is destined to become Orange Pearl Voice.

Kaito Domoto
Kaito is a junior high school student, in the same class as Lucia. He is strong, handsome, a phenomenally talented surfer, and widely worshipped by girls of all ages - and he knows it, too. Kaito's ego, however, may be largely a front that hides his feelings of fear and insecurity.His parents, both famous musicians, died when he was young, and he has been living on his own since then. Since Lucia appeared in his life, Kaito has been having frightening dreams, a glowing sigil sometimes appears on his forehead, and he occasionally exhibits strange powers. Kaito's greatest fear is that he might not actually be human.Kaito was saved from drowning by a mermaid seven years ago, and he has spent his life searching for that mermaid. Now that he's seen her again, he has become obsessed with his mysterious mermaid. At the same time, however, Kaito has grown increasingly fond of this cute, sweet girl in his class, named Lucia. Now Kaito also fears that his heart will eventually have to choose between Lucia and his beloved mermaid.Kaito doesn't know that Lucia was the mermaid princess that he like.In the end of pichi pichi pitch,Kaito find out that Lucia is the mermaid princess that he likes.
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Story
Lucia, Mermaid Princess of the North Pacific Ocean, sets out to land to find the boy she saved from a shipwreck seven years before the beginning of the story, the boy to whom she entrusted her pink pearl. She eventually found the boy: a surfer named Kaito Dōmoto. But as the human form Lucia assumed, a girl named Lucia Nanami, bears very little resemblance to her mermaid form, Kaito cannot recognize her. She cannot tell Kaito who she really is; otherwise, according to mermaid folklore, she would turn into foam. So she tries to convince Kaito into figuring out who she really is (since the legend does not say anything about the other person discovering a mermaid's true identity by himself).

At the same time, Lucia has been told that a group of water demons or suiyō (水妖) have invaded the marine world and she must gather the six other Mermaid Princesses and their pearls to resurrect the legendary goddess Aqua Regina to stop them. To fulfill this, she joins forces with Hanon and Rina, Mermaid Princesses who came up to dry land, use their pearls, turn into singing idols, and use their voices as an offensive.