This is the story of Lumina a mermaid that lives in the sea with all her friends who she has fun with pretending to be a princess.
She has always dreamt about being a princess and tell her friend Kuda who is a little sea horse that she hopes someday she can meet someone from the castle.
Meanwhile in the Ocean Castle the King and Queen Nereo and Lorelei are sad because of the new born princess they lost and would have been the heir to the throne.
Caligo, a general with bad intentions makes them a proposal he wants them to consider making his son the heir, because they haven’t any more family and Caligo is the Kings cousin, Nereo and Lorelei consider him to be a legitimate successor and prepare a ball to announce their decision.
Even though Caligo is very anxious to make his dream come true and watch his son to become King, his son doesn’t seem to share his father’s dream ; Fergis doesn’t want to be King he is interested in plants and sea life ,he is a bit clumsy and has no choice but to obey his father.
Caligo visits Scylla and old witch that is Luminas aunt because he wants her to make a poison to give to the King once he has pronounced his son the heir to the throne; the old witch has to do as she is told, Lumina overhears everything.
The mermaid always accompanied by her friend Kuda asks Scylla to take her to the castle because she has been invited and wants to go, the witch tells her she shouldn’t go because it will be very dangerous.
Lumina and Kudu take off in search of the castle and get lost in the seaweed forest and it takes them forever to get out. Lumina is very desperate, she sees a light at a distance and knows they are close to the city.
They weren’t close to the city; they arrived to a very dangerous place that they must escape from.
It’s the day of the ball and Lumina arrives to the castle and is captured by Caligo who recognizes her as Scyllas niece and locks her up in a dungeon.
The old witch ruins Caligo’s plan and she drinks the poison instead of giving it to Caligo.
Lumina is able to escape thanks to Fergus help, she discovers that her magic pearls are the key to her true destiny; she saves the kingdom and cures her aunt.
Years ago in his attempt to be King Caligo paid Scylla to poison the new born baby girl!!! The true heir; Scylla couldn’t do it and raised the baby herself, she told Caligo the baby had died.
While the girl was growing up Scylla realized it was almost time to tell her the truth.
Lumina is recognized as the true heir to the throne the witch is forgiven and they all live happily ever after, well except for Caligo who was punished and never heard from again!