Within the enchanting underwater realm lies the captivating Hai Ying Bao, known as the Ocean Castle. Ling Haixin and Xia Fan, two human girls, stumble upon the Princess of the Icy Blue City, Na Xiya, and undergo a magical metamorphosis into fairies. United with Xiya, they safeguard both the human and sea realms, embarking on a quest to unveil the culprits behind the ocean's pollution.