Lukia's life has been decidedly more complicated since finding out she's a mermaid-and a princess-on her 17th birthday. She's duty-bound to marry a merman fiancé she's never met, even while her feelings for Kurosuna-kun continue to grow stronger and stronger. Meanwhile, the new king of the deep sea schemes to drag her down to his inky domain, and a mysterious and gorgeous new transfer student arrives in class to stir things up with Kurosuna-kun!