When Laurent lures Kurosuna-kun to his underwater lair with a promise to reveal the truth about his mysterious past, Lukia and her friends rush to the rescue-but soon find themselves captured instead! Trapped in an aquarium adorning Laurent's throne room, Lukia and Lucia are all out of options...unless, that is, they can somehow convince the fallen mermaid princess Seira to reject the darkness in her heart and help them. It's a long shot, but Lukia knows she and Seira have something in common that might help Lukia get through to her-their shared feelings for Kurosuna-kun.