Voice: Female Personality: Extremely powerful, ruthless, and deeply vengeful. Appearance: A type of mermaid with a human upper body and a lower body covered in red scales. She has black hair styled in twin-tails with buns on each side, adorned with red seashell hair ornaments. Her eyes are normally black but turn red when she is angry. She is a skilled singer and travels with the Mermaids. She attacks the islanders for a specific reason. While singing, she has the power to manipulate plants at will. (Reason: She is searching for the culprit on the island who ate a mermaid.)

Voice: Female Personality: Generally gentle and loves food, but possesses a dual nature that is ruthless toward enemies. Appearance: Human upper body with a lower body covered in red scales. She has red hair that reaches her chest and is slightly smaller than the Siren. Like the Siren, her eyes are black but turn red when angry. She travels with the Siren. There were originally three of them, but now only two remain. She provides chorus for the Siren's songs.

Futaba Voice: Boy Personality: Mature, calm, devoted, and acts as the narrator of the situation. Appearance: Short hair. An islander who is always with Hitoba. While fishing on a boat with Hitoba, they accidentally struck the Siren's tail while she was playing, injuring Futaba. Hitoba then fed him mermaid flesh. Futaba, hating the idea of living a long life alone, fed the same mermaid flesh to Hitoba as well. (They are keeping the fact that they have eternal life from eating a mermaid a secret.)

Hitoba Voice: Girl Personality: Emotional, easily panicked, proactive, and obsessive. Appearance: Bob cut with long strands tied on the sides. An islander who is always with Futaba. While fishing on a boat with Futaba, they accidentally struck the Siren's tail, injuring Futaba. Knowing that mermaids grant eternal life, she killed one of the three mermaids and fed it to Futaba. (They are keeping the fact that they have eternal life from eating a mermaid a secret.)

Shimajiro Voice: Male Personality: Reliable, kind, strong, and chivalrous. Appearance: An adult male with a mustache, wearing an apron that says "Proud of Our Taste." He is the owner of a shop that serves curry and clam miso soup. The shop, named "Shimajiro," is located deep in the forest.