Minor Villains

Several times throughout the series, one or more of the Main Antagonists summoned monsters in an effort to capture the mermaid princesses. In many cases these were powered up versions of real life sea creatures. These one-time villains are popular in similar shows such as Cardcaptor Sakura or Sailor Moon, with episodes containing them usually being called "Monster of the Week" episodes. Mainly Sheshe and Mimi created most of the one-time villains to use as their minions.

Water Dragons

Izuru and her water dragon

The water dragons are created by Izuru and often used to attack mermaids or humans. They are capable of travelling at a high speed and move high in the air, sometimes rushing quickly to terrify humans.

Izuru summons them from water sources, such as the ocean or from pools. The dragons are icy blue in colour with sharp teeth and seem to have a spiky and hairy texture. They don't have to be directly connected to the water source in order to attack, as they can move on their own or under Izuru's commands.

One of the water dragons is named "Mitato-tan", as mentioned by Izuru in Episode 45 after Mitato made Kashiwagi faint upon seeing it.

The water dragons also react to the Mermaid Princesses' songs, where they'll spiral out of control and try to escape. They react to the light of Kaito's Forehead Beam Power as well, and dissolve into nothingness when the light reaches them.

Tropical Fish

One of the tropical fish

The tropical fish in Episode 26

The tropical fish are Eriru's minions that she uses to locate mermaids. They appear in Episode 2 where Eriru was seen giving the fish away in plastic bags at the Spring Festival. Eriru says the tropical fish love good music and should be given to people who love music, though it is unknown if she said this just so the fish would have a higher chance to be given to mermaids. The fish have yellow, black and white stripes, their eyes will glow red once they detect a mermaid, Eriru will be alerted of the fish's findings.

Eriru had shoved one of the fish to Tarō, and later on when he bumped into Hanon, he gave it to her instead. Not long after, Hanon set the fish free into the sea. Upon diving into the sea and transforming into a mermaid, the tropical fish followed her, letting Eriru know her location to capture her.

The fish are seen again in Episode 26, where Eriru had sent them out all over the seas to search for the Mermaid Princesses. One of them followed Rina when she was in the sea, looking for Noel. This time the fish had a slightly difference appearance, having only yellow and black stripes. The fish came back to Eriru to tell her that it had found the green pearl princess.

Tachi Brothers

The three main Tachi brothers

The extended Tachi family

Appearing in Episode 43, the Tachi Brothers are a group of largehead hairtail fish who were summoned by the Black Beauty Sisters to track down and capture the Mermaid Princesses. They planned to do this by toying with their emotions and demoralising them, making them easier to capture. After cornering Lucia and Hanon with a water gun and causing them to fall off a cliff into the ocean. The brothers then engaged the mermaids, summoning several more of their brothers in an attempt to capture them, however they were swiftly defeated.

The brothers were voiced by:

• Japanese: Daiki Nakano (Red), Naoki Kinoshita (Blue), Tatsuhisa Suzuki (Green), Daisuke Kishio (Fourth Brother)
• Spanish: Mariano Garcia (Red), Javier Balas (Blue), Juan D'ors (Green)
• Italian: Renato Novara (Red), Massimo Di Benedetto (Blue), Giuseppe Calvetti (Green), Ruggero Andreozzi (Fourth Brother)
• Cantonese: 陳卓智 / Chan Cheuk Chi (Blue), 蘇強文 / So Keung Man (Green)

Lionfish

The Lionfish

The Lionfish is a fish that Sheshe and Mimi used in Episode 54. Sheshe created a fake version of Kaito's pendant and ordered the fish to use it to lure Lucia away. When it found Lucia, it swam near her to get her attention. Lucia noticed what seemingly looked like Kaito's pendant on the fish's back, she desperately followed it, hoping for the Lionfish to lead her to where Kaito was.

Eventually, the Lionfish swam inside a cave until they reached a dead end. Lucia was starting to feel suspicious and asked the fish if that's where it really found the pendant. Upon touching the Lionfish, the pendant dropped to the floor, revealing it was just a fake pendant.

Due to Lionfish being a type of venomous fish, Lucia fell victim to its poisonous spikes, the poison numbed her body and she couldn't move. The Lionfish began to swim out as it saw Lucia losing strength, leaving her for dead as a volcanic eruption threatened to collapse the cave and bury her alive.

Galeos

Galeos searches for the Mermaid Princesses

Galeos was created in Episode 55 by the Black Beauty Sisters. He was originally a remora which was empowered and given a form somewhat resembling a humanoid merman, then tasked with infiltrating the human world and locating the Mermaid Princesses. It was revealed that Galeos possessed some form of psychic mindreading ability, as he was able to capture Momo and read his mind, discovering that the Mermaid Princesses did frequent the nearby seas.

Upon learning this from Momo, the Princesses then patrolled the area searching for the demon, however they were unable to find him. Later that evening Hanon (Who was now alone) noticed that Galeos had been following her for some time and tried to evade him, but was unsuccessful. She then tried singing to defeat Galeos, however the demon was given special headphones that allowed him to negate a Mermaids song. The chase continued throughout the night and as morning broke, and Hanon was exhausted, the Black Beauty Sisters appeared to capture her. Unfortunately for the villains, Lucia and Rina appeared at that moment and sang together, with Galeos attempting to use his headphones again, but Hippo snatched them away forced him to listen, and Galeos turned back into a normal remora at the end.

Galeos was voiced by:

• Japanese: Ken Takeuchi
• Spanish: Rais David Báscones
• Italian: Diego Sabre
• Cantonese: 馮錦堂 / Fung Kam Tong
• Taiwanese: 林谷珍 / Lin Ku Chen

Sardines

The sardines

A large group of sardines were used to assist the Black Beauty Sisters' plan in Episode 56. One particular sardine was given a whistle to call forth other sardines, and they would join together to appear in the shape of a whale. The plan was to use the sardines to lure out Rina, as she would have thought that the "whale", was Minke.

Later on, the sardines were "defeated" when Hanon flicked one of them on the head. They danced along to the mermaids' songs, and parted when the song was over.

Mehikari

Mehikari about to attack the mermaids

Mehikari's human form

Mehikari is a greeneye fish that was used in Episode 57. His purpose was to distract the Mermaid Princesses from singing with his sad music and bright light. Mehikari's eyes can glow in the dark as he's a fluorescent type of fish, which creates a light that appears almost blinding to the mermaids.

While on land, Mehikari takes the form of an old man, continuously playing his accordion on the street. His accordion makes passersby feel a sudden urge of melancholy and sadness.

Mehikari was voiced by:

• Japanese: Hajime Iijima
• Cantonese: 譚炳文 / Tam Ping Man
• Italian: Massimo Di Benedetto
• Spanish: Jesús Rodríguez

Beyrich's Slit Shell

Beyrich's Slit Shell

Beyrich's Slit Shell is a big mollusk that appeared in Episode 58, requesting to be the Black Beauty Sisters' lackey. Sheshe ordered it to give the Mermaid Princesses a bit of trouble.

When Lucia became upset and dove into the Ocean, Beyrich's Slit Shell used its tentacles to restrain her tail. By the time Hanon and Rina arrived at the scene, Lucia was half-unconscious and restrained by Beyrich's Slit Shell. They sang Ever Blue and Kodou to defeat it.

Sea Snake

Sea Snake attacking Lucia

The Sea Snake is a male sea snake that the Black Beauty Sisters used in Episode 59. The Sea Snake helped bring the two sisters to the Indian Ocean.

After Sheshe and Mimi sang to Lucia, Sheshe ordered the Sea Snake to attack her. He coiled himself around Lucia until she had no strength left to resist.

He disappeared after his job with the Black Beauty Sisters was done.

Giant Jellyfish

The Giant Jellyfish

The Giant Jellyfish was a jellyfish that the Black Beauty Sisters used in Episode 60.

The Giant Jellyfish is large in size and can electrocute anyone that swims near it, it can also trap people inside like it did to Lucia. When the Mermaid Princesses sing, it converts their song into energy. The Giant Jellyfish ended up being overpowered with energy and exploded.

Clione (Ice Fairy)

Demon Clione

Clione

Clione is an ice fairy that Michel captured for the Black Beauty Sisters to use in Episode 62. She is very small in size and has ice powers, she was temporarily hypnotized and turned into a water demon.

Lucia and Hanon came across Clione on their way back home in the ocean, they were surprised since ice fairies are usually found in the Arctic Ocean. They were fooled by Clione's harmless appearance, and she suddenly turned into a big pink and blue manta ray demon. The transformed ice fairy flapped her wings repeatedly to freeze Lucia and Hanon in place, giving an opportunity for the Black Beauty Sisters to show up and sing to them.

Eventually, Rina came to rescue the two of them and sang back at the Black Beauty Sisters, Clione returned back to her normal self and thanked the Mermaid Princesses for saving her.

Sea Cucumber

Sea Cucumber

Sea Cucumber's Demon Form

The Sea Cucumber is a creature summoned by Mimi in Episode 65 after Sheshe desperately begged her to come up with a plan. Mimi requested the Sea Cucumber to do something to lure the Mermaid Princesses out.

The Sea Cucumber soon arrived at the place where Lucia and Hanon were, using his sense of smell to detect mermaids.

When it was wriggling on the floor, Hanon thought it looked gross and Lucia poked it with a stick.

The Sea Cucumber was enraged and turned into a large monster. However, Lucia and Hanon defeated it by singing Mizuiro no Senritsu, and the Sea Cucumber apologized and left.

Bubble Crab

Bubble

The Bubble Crab is a giant crab that Sheshe summoned after popping Mimi's bubble wrap in Episode 69, she told Bubble to use his ability to scare the humans.

Once Bubble was on the beach, he began using his power to create bubbles to trap people inside. Hanon was walking along the beach and saw this scene happen, she transformed and was about to fight him. Lanhua showed up not long after, Lucia and Rina arrived at the beach too. As Lanhua was singing in her chibi forms, Bubble became affected by the song like the Mermaids and began spewing bubbles that trapped the Lanhua chibis. Bubble was defeated and disappeared after the Mermaid Princesses sang.

Kraken (Squid)

Kraken is an enormous white squid that appeared in Episode 81. It is unknown whether this minion is real as it only appears in Sheshe and Mimi's nightmare. It is also likely that this is not the legendary sea monster Kraken, but rather just a typical sea squid that Sheshe and Mimi turned into their minion.

In Sheshe and Mimi's nightmare, Sheshe orders the Kraken to snatch away the Mermaid Princesses' microphones. The Kraken obeys and uses its tentacles to knock their microphones down into the abyss.

Hippo took the microphones into his hands and transformed into an idol, he "defeated" Sheshe and Mimi.

Napoleon Fish

“	The word "Impossible" is not in my Dictionary.	”
–Napoleon Fish, Episode 81

Napoleon Fish is a Humphead Wrasse that was created by the Black Beauty Sisters in Episode 81. He is named after the French general, Napoleon Bonaparte, supposedly because he can come up with good battle plans.

Throughout the episode, he comes up with various plans for the Black Beauty Sisters, Lady Bat, Lanhua, and Alala to capture Hippo instead of the Mermaid Princesses. He intended to use Hippo as bait for luring out the Mermaid Princesses.

Soon after they captured Hippo, he appears in the tower that Sheshe and Mimi created as the battleground for the Mermaid Princesses. He encountered the Mermaid Princesses on the fourth floor after they got past Alala, Lanhua, and Lady Bat, where he bragged about his battle plan. However, the trio wasn't amused and threatened to rip off his scales unless he told them where Hippo is, leading him to reveal that Hippo is on the top floor.

On the final and upper ground of the tower, Napoleon Fish helped the Black Beauty Sisters by tackling the Mermaid Princesses from the back, causing them to lose their microphones, leaving them unable to sing.

After the Mermaid Princesses got their microphones back and sang, Napoleon Fish was defeated and retreated along with the Black Beauty Sisters. He presumably left but forgot his dictionary, which Sheshe decided to put the word "impossible" into it.

Napoleon Fish was voiced by:

• Japanese: 桜井敏治 / Sakurai Toshiharu
• Cantonese: 林保全 / Lam Pou Chuen
• Taiwanese: 賀宇傑 / Hè Yǔ Jié
• French: Jean-Paul Clerbois
• Hebrew: גלעד קלטר