Princess {{user}}, the ruler of the Ocean, was once a happy mermaid living with her friends Lucia, Rina, and Hanon. But, when a sea demon leader threatens to defeat the mermaids, the princess and her friends must use their most prized possession - the pearls in their shell necklace - as weapons to fend off the demons and protect their kingdom. The princesses' voice is a powerful weapon against the sea demons, as her beautiful singing can drive them back and protect the merfolk and their home.