1(53). "Morning of Separation"- Taro Mitsuki announces his plans of heading to Germany, leaving Hanon disappointed. Kaito flies to Hawaii after spending a night with Lucia and saying goodbye to her. Lucia sees the image of a young mermaid in her dreams. Lucia, Hanon, and Rina face a new foe.
2(54). "That Horizon- Lucia gets a phone call saying that Kaito was lost at sea and sets out to the open sea to search for him.
3(55). "Aquamarine Melody"- Hanon wants to say good bye to Taro-chan, but she gets stalled. She reaches him at last and gets a present from him.
4(56). "A Premonition of Happiness"- Rina gets a letter from her whale friend, saying she should go home. She changes her mind in the last second.
5(57). "Maestro"- Hanon and Lucia go to a concert, where Rihito conducts an orchestra.
6(58]. "The Young Man"- Kaito has finally returned, but he has lost his memories. To make things worse for Lucia, he is with another girl. Hanon has also found herself a suitor.
7(59). "Her Stolen Heart"- Lucia pinpoints the location of Seira's spirit. But before Seira's spirit merges with the orange pearl, Michel absorbs Seira within himself. Lucia must now collect the falling heart fragments of Seira, in order for her to be brought back to life.
8(60). "The End of the Memories"- In an effort to have Kaito's memories returned, Lucia, Hanon, and Rina let him take up surfing lessons again.
9(61). "Love Etude"- Hanon decides to play the sheet music Taro Mitsuki gives her. She however can't play the piano, so Nagisa buys her a piano book to help her, only to have Kaito help her instead. This episode introduces Lady Bat, a new villain, and Hanon's new image song, Mizuiro no Senritsu.
10(62). "Leftover Feelings"- Rina returns to her country in the North Atlantic Ocean to attend a ceremony there. But she also starts to miss Masahiro and ends up missing something very important from him.
11(63). "Her Brother's Feelings"- Lucia, Hanon, and Rina hang out with Kaito and Michal around town by shopping.
12(64). "The Marine Mermaid's Light"- Coco invites Lucia, Hanon, and Rina to come with her to the Indian Ocean to help search for the Legendary Spiral Shell. It turns out to be Sara's shell that held all of her memories, and the four (also Hippo) battle the Black Beauty Sisters for it.
13(65). "His Secret"- Rina wants to know more about Masahiro after Hanon shows her a picture of him and his rich father in a magazine. She asks him to let her know more about him.
14(66). "Voice From The Dark"- This episode introduces Lanhua, a new villain. Aqua Regina appears and gives the Mermaid Princesses a new song.
15(67). "Prayer of the Seven Seas"-Lucia, Hanon, and Rina head for Antarctica after recent events there worry Caren.
16(68]. "It's Summer Vacation! Let's Gather, Everybody!"- In order for Maki's beach house to compete with a nearby hotel, Lucia, Hanon, and Rina hire Caren, Noel, and Coco to help them in their chores. The six Mermaid Princesses engage in a beach volleyball match against some guests of the hotel.
17(69). "A Midsummer's Night Celebration"- Nagisa obtains a pair of gala tickets from Masahiro and decides to take Hanon out. But his plans to have Hanon's consent end up with him being played around by Coco, Noel, and Caren in order for Hanon to realize her true feelings for Nagisa.
18(70). "Star Labrinth"- The six Mermaid Princesses find themselves in a magical world as a mysterious event grants two wishes at the same time.
19(71). "Song of Healing"- The King of the Squids, Somegorō, asks the Mermaid Princesses for help as his people are being terrorized by the Black Beauty Sisters.
20(72). "Love Detectives"- To find out why Masahiro likes Rina so much, Caren dates with him while Coco and Noel watch from the sidelines, keeping Lucia and Hanon out of the fray.
21(73). "Love Intrusion"- Lucia accidentally finds her keys to Kaito's house and remembers the promise to keep his house clean while he was gone. When she is cleaning the bathroom, Lucia accidentally gets wet and decides to take a bath. Meanwhile, Kaito realizes that someone is in his house... Also, Alala gets introduced in this episode.
22(74). "Robber of Memories"- Coco, Noel, and Caren leave. Lucia then gets a strange box from Rihito. Later, Lucia, Hanon, Rina believe that there is a robber at Pearl Piari so they decide to set up traps; the box gets stolen however and Lucia looks all over town for it. In the end, it turns out that Rihito himself stole the box.
23(75). "Feelings Inside"- Lucia, Hanon, and Rina are invited to a concert wherein Rihito conducts an orchestra. During the performance, Rihito's power is suddenly revealed. Meanwhile, the all of Michel's minions are given a new power made from a part of Seira's heart. All five surround the concert hall, singing, causing the concert hall to begin crumbling, after Rihito stops using his power to keep the building together. Lady Bat, Lanhua, and Alala leave when it seems like the plan failed. The Black Beauty Sisters use their new power to create a new 'dimension' and 'clones' to sing another song. (The originals are also singing.) Suddenly, Aqua Regina appears and give the mermaids a new song.
24(76). "I Wish..."- To cheer Lucia up, Hanon and Rina take her to a karaoke joint, which just happens to have their songs. They sing and get horrible scores on their own songs! Being angered by that, the three transform into their idol forms and sing, causing Lanhua (who was the cause of everything) to go and try and capture them.
25(77). "Love Fortune"- Hanon tries to cheer Lucia up by bringing her to a fortune teller. The fortune teller tells Lucia to throw her most precious item in the sea (which is her ring). Lucia does so, but then the next day, it turns out to be a fake. Lucia goes into the sea to retrieve her ring. She is almost captured by Lady Bat (who was the fortune teller) before Hanon and Rina arrive.
26(78]. "Idol Debut"- A man goes around looking for people to be idols. He asks Alala (who is in human form and accepts) and Rina. Rina (who is with Masahiro at the time) looks at the poster, before Masahiro grabs it out of her hands and rejects. When Masahiro sees Rina staring at a poster of Alala, who became a new idol, he thinks he ruined her dream of becoming an idol. The three mermaids end up at the concert and defeat Alala.
27(79). "Separated Sisters"- After another loss at the hands of the Three Mermaid Princesses, the Black Beauty Sisters bicker at each other because of Fuku's comments. Mimi leaves Sheshe during their argument because Sheshe kept on blaming it on her. Mimi tries to capture the mermaid princesses on her own, and fails, almost dying. Sheshe uses the new power given to them by Michel to heal Mimi, as she doesn't care if they get 'kicked out' or not; she would rather die in the sea with her sister.
28(80). "Seira's Flower Garden"- Lucia's class takes a trip to a greenhouse. Lucia's spirits start to brighten as Kaito sits beside her. Seira's spirit alerts Lucia, Hanon, and Rina of an impending danger.
29(81). "Gloom By A Triple Threat"- The Black Beauty Sisters, Lady Bat, Ranfa, and Alala hatch up plans to capture Hippo and use him as bait for the Mermaid Princesses.
30(82). "Embrace Me..."- Rina still cannot confess her feelings to Masahiro because of her identity, however Rina learns how strong her feelings were for Masahiro.
31(83). "The Last Love Letter"- Hanon begins to meet Nagisa more. But her feelings have become torn as she receives a love letter from Taro Mitsuki, her former music teacher.
32(84). "Memories Vanished At Sea"- Lucia is slowly convinced that Kaito's memories have fully returned. But Michel tries to make sure Kaito's previously lost memories remain lost.
33(85). "Confused Heart"- Lucia cherishes her reunion with Kaito. Meanwhile, MiMi becomes torn between duty and friendship as she slowly discovers her enemies' human identities.
34(86). "Temptations of a White Feather"-Michal becomes hysterical as Kaito leaves her for Lucia. A mysterious voice urges Michal to follow it.
35(87). "Instead of Goodbye"- Michal decides to "end her pain and sadness" by becoming one with Michel. Lucia, Hanon, Rina, and Kaito go to stop her, but they arrive too late. Lady Bat, Lanhua, and Alala team up to stop the mermaids, if only for a moment. The connection between Michal and Michel is revealed.
36(88]. "The End of Despair"- Michel takes the three mermaids into his dimension and begins to fight them. Seira stops him with a song. Michel absorbs Lady Bat, Lanhua, and Alala. But not before, the three villains reveal that Michel is just like them.
37(89). "To The Castle in the Sky"- Without any villain attacks for a while, Lucia, Hanon, and Rina spend more time with their boyfriends as their relationships start to grow further. Caren, Noel, and Coco return. Meanwhile, Michel is told that his true self is a statue. The six mermaids make their resolve to save Seira from Michel, but they are overpowered. Seira asks Lucia to break the statue that is Michel's true self.
38(90). "Battle on Christmas Eve"- The six Mermaid Princesses, together with Rihito and Kaito, engage on a final battle with Michel. Seira is finally born, ready to fight with her voice. The Great One turns out to be Rihito and Michal's father; everything is explained, and the Great One destroys the statue that is Michel's true self. After that, Fuku reveals that he was created to control Michel, should anything go wrong; he does so, but the mermaids still sing a powerful song to defeat him. Aqua Regina makes an appearance and their song gets through to Michel and Michal. The spirits of the original angels appear and invite Michel and Fuku to join them, which they happily accept. In the end, Aqua Regina gives a reborn Michal to Rihito.
39(91). "Yume no Sono Saki He"- With all things troubling themselves and the marine world out of the way, the seven Mermaid Princesses celebrate the newfound peace by organizing a little concert—one that becomes a huge reunion of characters from the entire series.
