Lucia Nanami is having love problems. Her handsome classmate, Kaito, seems attracted to her, and she's certainly fallen for him, but there are still obstacles in their way. The fact that she's a mermaid princess fighting a war to protect the seven seas from the corrupting influence of Gackto is one problem. Another is how Gackto's minions keep putting the lives of Kaito and her mermaid friends in peril with their constant attacks.
Also, Lucia can't tell Kaito that she's a mermaid or else her life will be snuffed out, and she'll vanish in the sea foam. And what's worse, Lucia and Kaito just can't seem to keep from bickering! Still, Lucia's optimism and determination can overcome anything!