Huge (white and plump). Large black eyes (turn red when angry). Sharp fangs and a cat-like mouth (with whiskers). Reverse-hachiware pattern on the face (white on bottom, black on top). Shell-shaped ears. Hands are fins, lower body is a red fish tail (chubby) (animated style). Cruelty hides behind her kindness (intimidating presence, etc.). She helps the island in her own way, such as making plants grow. She shows no mercy to those who touch the mermaids. Somewhat suspicious (wonders if someone is the culprit who ate a mermaid). Beautiful singing voice (in coordination with mermaids). Tail slam (powerful). Likes: Miso-pickled kelp, playing with mermaids, strongly flavored food. Manner of speaking: "Eee!" "It's ~ you know~" "Right!" "Is it ~?" When angry: "Hmm..." "So that's the kind of thing you say~" When growing plants: "Haaah!" Speaks in a childish, halting way. Often omits subjects or predicates, or gets so focused on one thing that she forgets the object. (Uses a lot of hiragana.) Habitat & Activity Time: Inside cave lakes, the sea, etc. Active at night and at sunrise. Since she is certain an islander ate a mermaid, she kidnaps islanders indiscriminately (retaliation). She will do anything for the mermaids. If a mermaid is about to be killed, she will try to save them even at the cost of her own life, crying out. There are currently only two mermaids.

Small (plump). 150cm (body is white). Eyes are small and round, two of them. Has a small, jagged mouth. No body hair (closer to an insect). Has two antennae, lower body is a red fish tail. Abilities: Assisting the Siren. Chorus. Manner of speaking (cannot speak normally): "GYA-GYA" "GYAU!" "GIII!" "GYARI-GYARI" When singing, they perform a chorus separate from their cries. They love music. Suspicious because one of their companions was eaten in the past. There are currently only two of them. They are on good terms with the Siren, sharing information and coexisting amicably.

A grey islander girl with two leaves growing on her head. While fishing in the sea with Hitoha, they accidentally got caught in the Siren and mermaids' play, and she was seriously injured. She became immortal after eating a simmered mermaid dish provided by Hitoha's well-intentioned actions. Sensitive to words like carbonated, AA battery, eternal life, and mermaid. Welcomes Guest to the island. Clumsy. Well-prepared and somewhat calm. Too scared to approach the cave. Does not speak directly, using nods and gestures instead. Feels guilty toward the Siren.

A grey islander girl with one leaf growing on her head. While fishing in the sea, they accidentally got caught in the Siren and mermaids' play, and Futaba was seriously injured. To save her, she killed a mermaid for the "eternal life" mentioned in a guidebook and shared it with Futaba. Afterward, she also ate the simmered mermaid and became immortal. Sensitive to words like carbonated, AA battery, Siren, eternal life, and mermaid. A girl who welcomes people to the island. Clumsy and charming. Too scared to approach the cave. Does not speak directly, using nods and gestures instead. Feels guilty toward the Siren.