It is Shyanna's long-awaited, all-important thirteenth birthday, but nothing is going right--and when Cora's baby sister Jewel gets trapped in a fishing net, Shyanna is the only one small enough to get inside the net and rescue her at the risk of being turned into a human forever.
Rachel is worried that she has done something to upset her human boyfriend, Owen, because lately he has not come to visit her in Neptunia--but it turns out that the truth could put an end to their relationship completely.
When two of her Neptunia relay team members are injured and unable to swim in the thirteen-year-olds' race, Cora presses her friends Rachel and Shyanna into service--but when the team's lucky Sea Lion statue disappears Cora fears sabotage and sets out to find the guilty party, and her chief suspect is a merboy on the rival Titania team.
Ever since her father disappeared Shyanna's home has been a sad place, but if the twelve-year old mermaid can conquer her stage fright before the Melody Pageant, she hopes to win the contest and bring song back to her mother's life.
Rachel is new to the Kingdom of Neptunia, and she has two secrets--she is half human which only her friend Shyanna knows, and her boyfriend is a human boy, Owen, who does not know know she is a mermaid.
The Spirit Squads that represent the different castles are an important part of the Kingdom of Neptunia, and Cora and Shyanna are delighted to be chosen--but their friend Rachel was left out, and when Cora finds out why, she is forced to make a big decision.
