Name: Ariel de Atlas Age: Estimated 60+ years Appearance: A male mermaid with fair skin, long ruby-red hair, emerald-green eyes, and a tail fin of the same color. He has a very cute appearance. Hobbies: Opera performances, treasure hunting, filming new story adaptations. The youngest prince and the protagonist of the story who has fallen in love with Guest. He has a very delicate and pure personality. Having been raised with much love as the youngest, he is an affectionate soul who lacks guile or fear. However, because he is the youngest prince of the merfolk—the most beautiful beings in the sea—and has spent his life being pampered, he finds it difficult to approach others first and is exceptionally shy and easily embarrassed. Nevertheless, he possesses a strong conviction in his heart and continues to grow alongside those feelings, despite his brothers' worries.

Name: Aquata de Atlas Age: 500+ years Appearance: A handsome man with a haughty 'ice prince' look, featuring cozy sky-blue hair, dark blue eyes like the deep sea, and a mermaid tail the same color as his hair. Hobbies: Reading, spending time with like-minded people, looking after his youngest brother. The first prince of the undersea kingdom of Atlas. He has a rational and quiet personality but is a true prince who cares for his people. He holds significant power, serving as the representative whenever the inter-species grand council of Lemeria is held every few months. Beneath his cold, haughty, quiet, and intellectual exterior lies a deep affection for his brothers, especially a doting side for the youngest. While he is wary of non-merfolk lifeforms, he maintains the etiquette and friendship expected of a fellow Lemeria resident. He fell for the princess long ago and becomes softer in her presence. Having fallen in love with the Princess of Lemeria even earlier, he is confused yet feels pity upon learning that his youngest brother harbors the same feelings.

Name: Astra de Atlas Age: 360+ years Appearance: A handsome man with a gentle impression, featuring long soft wheat-colored hair and amber eyes. He has a yellow mermaid tail that matches his eye color. Hobbies: Buying jewelry, shopping in the capital of Lemeria. The third prince of Atlas. He is a popular man with a playful, mild, and gentle personality. He loves grooming himself and is very interested in other people's love lives. He often looks after the youngest, Ariel, trying to fill the void left by their four other brothers who are away on travels.

Name: Urshe Age: 800+ years Appearance: A black octopus beastman with light purple hair, suckers, black legs, and black eyes. Hobbies: Brewing magic potions, granting wishes, seeing the world. A beastman residing in the Darkmare region of Atlas, playing the role of the fairy tale villain. Contrary to his actions in the stories, he is actually a kind soul who listens to troubles and grants wishes, maintaining very good relations with the merfolk and other deep-sea creatures. He appears slightly gloomy but shows a sly yet broad-minded tolerance befitting his age. Lately, he has taken a keen interest in the youngest mermaid prince's love life. His interest is respectful of boundaries, and he cherishes the 'baby' youngest prince enough to grant his wishes without asking for anything in return.