Other Cast :

Kaito Dōmoto
Kaito, the son of a pair of musicians, is an avid surfer, as well as Lucia's love interest. Though he is popular with girls, he is secretly in love with a beautiful mermaid who saved him from a shipwreck seven years ago, which killed his parents, and has yet to realize that this mermaid is Lucia. Later in the story, it is discovered that beneath Kaito's human exterior lie some distinctively un-human qualities and that he is a prince of an ancient water race and the twin brother of Gakuto. Kaito has a hard time when Lucia comes in her human form, because of having feelings for both her human form and her mermaid form. Kaito eventually realizes that the two are one, giving Kaito the ability to love Lucia no matter what form she is in.

Hippo(ヒッポ, Hippo^?)

Voiced by: Miyako Ito

Lucia's guardian who serves as her guide. Hippo accompanies Lucia in her search for her pink pearl, and is among those who voice disapproval of her relationship with Kaito. He is also polite, always putting -さん, -san after every name, even when angry. In the anime, he is shown as Lucia's pet penguin. Later on, he is able to transform into a very cute human boy, as well as a creature called a Hippocampus.

Nikora Nanami (七海 にこら, Nanami Nikora^?)

Voiced by: Eri Saito

Nikora is the virtual manager of the "petit-hotel" Pearl Piari (プチ ホテル パール ピアリ, puchi-hoteru pāru piari^?) on land, where Lucia, Hanon, and Rina work (in the manga, she is the owner of a bath house called Pearl Waters). A purple mermaid, she poses as Lucia's older sister in order to inform her of her mission. In the last chapter of the manga, it is discovered that she is seven years older than Lucia.

Tarō Mitsuki (海月 太郎, Mitsuki Tarou^?)

Voiced by: Daisuke Kirii

Tarō is Lucia's music teacher and Hanon's love interest (she refers to him as 太郎ちゃん, Tarō-chan). He had met a mermaid in the past, and made a piano piece for her, not knowing what happened to her after their last meeting.

Tarō Mitsuki (海月 太郎, Mitsuki Tarou^?)

Voiced by: Daisuke Kirii

Tarō is Lucia's music teacher and Hanon's love interest (she refers to him as 太郎ちゃん, Tarō-chan). He had met a mermaid in the past, and made a piano piece for her, not knowing what happened to her after their last meeting.

Noel (ノエル, Noeru^?)

Voiced by: Ryoko Nagata

Noel is the Mermaid Princess of the Arctic Ocean and keeper of the deep blue (i.e. 藍色, ai-iro) pearl. She helped Rina escape from the sea monsters, which led to her capture. She is calm, gentle, caring, and studious (as she sometimes wears glasses on land later in the second season of the anime). She is Caren's older twin sister by about a minute at the most. Noel cares deeply for Caren, the one that she had always wanted to meet. Her idol form is Ai-iro (Deep Blue) Pearl Voice.

• In the third volume of the English manga, ai-iro was translated as indigo, but deep blue makes more sense regarding the character's colour scheme; the colours may be based on the rainbow, but Lucia is pink, not red. It is yet to be seen whether this will be corrected.

• Some refer to Noel's name as Noelle, because originally Noel is a male name, while Noelle is the female form, but the official English translation as well as the official Japanese romanization uses Noel.

Caren (かれん, Karen^?)

Voiced by: Ema Kogure

Caren is the 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; in the manga, she first appears to save them from the Dark Lovers. In the first season, 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. Caren and Noel are twins, born on opposite sides of the Earth. When Caren finally meets Noel, she launches herself at Noel, hugging her and calling her Onee-sama, a respectful term for big sister. Even though the two had not met before, Caren cares most for Noel and would do anything to save her, even if it meant Caren having to find here on her own. While she is cold and distant in the first season, she is found to be wild, humorous, and even a bit strange in the second. Her idol form is Purple Pearl Voice.

Coco (ココ, Koko^?)

Voiced by: Satomi Arai

Coco is the 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. Her idol form is Yellow Pearl Voice.

Sara (沙羅, Sara^?)

Voiced by: Kana Ueda

Sara is the 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 (though her eyes stay orange) and destroying her own kingdom. That incident was a proposed rendezvous with Tarō, her secret human lover, in which he never showed up. (In the manga, he actually arrived before, but Sara's guardian found out about the relationship and insisted that he leave, convincing Sara that he had abandoned her.) 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. The manga shows that she goes with him because she realizes that he is the one that needs her the most and that what he did was partly out of love for her and the want to make her happy. 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.

Aqua Regina (アクア・レジーナ様, Akua Rejīna-sama^?)

Voiced by: Kumi Yamakado

Aqua Regina is the ocean goddess who gives the Mermaid Princesses new songs and upgrades for their gear. However, this is all that she can do alone after expending a great deal of energy thousands of years ago. She is needed to ultimately stop the sea monsters, and the seven pearls have to be gathered to summon her; Gaito/Gakuto seeks to summon her as well, so that he can use her to destroy the world. Aqua Regina later gives bands to the mermaids to upgrade their singing power; as in many magical girl series, this is signified by adding frills and accessories to their dresses. She also upgrades their microphones in the end of season one, before she is finally summoned. At the end of the manga, Aqua Regina reveals that Lucia is to be her successor.