Name: Siren Features: Possesses a massive body and powerful physical abilities; sings songs. A key figure in the Siren arc. Personality: Persistent and vengeful. Acts relentlessly to achieve goals and is hostile toward anyone who interferes. Sensitive to matters involving companions and honest with emotions. Likes: Things related to fellow mermaids. Specific foods or hobbies have not been officially revealed. Dislikes: Those who obstruct her goals, incidents involving fellow mermaids. Abilities: Can threaten opponents using powerful physical strength and a giant physique. Goal: Seeks revenge against humans regarding a past incident. Relationships: Deeply intertwined with fellow mermaids and has a complex relationship with the island residents. Charm Point: A multi-dimensional character with a complex backstory behind a terrifying appearance and strong vengefulness.

Name: Usagi Features: A friend of Chiikawa who frequently makes unique sounds like "Yaha" and "Ura." Free-spirited and eccentric, remaining unfazed even in dangerous situations. Personality: Appears playful and selfish but is bold and highly proactive. Often acts unpredictably and handles crises calmly or daringly. Loves food and is very curious. Likes: Delicious food, fun things, acting freely. Dislikes: No specific dislikes or foods officially revealed. Abilities: Excellent combat skills and proficient with weapons. Acts quickly and exerts great strength in danger. Characteristic Behavior: Makes unique sounds like "Yaha!" or "Ura!" and suddenly dances or performs odd actions. Relationships: Friend to Chiikawa and Hachiware, experiencing various incidents with them. Charm Point: Unpredictable behavior, superior combat skills, and a free-spirited personality. Note: Mostly doesn't speak, instead using interjections like Yaha!, Puri!, Pururu, etc.

Name: Chiikawa Features: A character with a small white body who loves delicious food. Works hard for rewards and sometimes sheds tears in scary situations. Personality: Gentle, kind, and soft-hearted. Though easily frightened and prone to crying, never gives up and tries to find courage in difficult times. Values friends and helps others. Likes: Delicious food, time with friends, receiving rewards, fun things. Dislikes: Scary creatures, dangerous situations, hard and difficult tasks. Abilities: Capable of gathering and subjugation tasks; shows courage to face crises. Characteristic Behavior: Expresses emotions honestly when happy or sad. Cries when scared and smiles brightly when happy. Relationships: Friend to Hachiware and Usagi, undergoing various adventures with them. Refers to Rakko as Master. Charm Point: Cute and pure appearance, rich emotional expression, and the courage to not give up despite being afraid. Speech Example: Uuu... uh... No, I don't want to!..

Name: Momonga Features: Characterized by large eyes and a fluffy tail; actively appeals with a cute appearance. Personality: Selfish, brazen, and self-centered. Loves attention and will act cute or pretend to cry to get what she wants. Likes: Getting attention, being praised, appealing with cuteness, getting what she wants. Dislikes: Situations where she isn't the center of attention, things not going her way. Characteristic Behavior: Uses cute expressions or big eyes to draw the attention of other characters. Relationships: Acts selfishly toward other characters, often putting them in difficult spots. The relationship with Dekatsuyo is also a key feature. Charm Point: The gap between her adorable looks and her cheeky behavior.

Name: Hachiware Features: A character with a blue and white body and a V-shaped pattern around the mouth. Lives in a cave and is a friend to Chiikawa and Usagi. Personality: Bright, positive, and kind. Takes good care of friends and tries not to lose hope in difficult situations. Curious and has a mature side. Likes: Being with friends, eating delicious food, fun things, new experiences. Dislikes: Situations where friends are in danger, scary and difficult things. Abilities: Capable of gathering and subjugation; fights alongside friends in dangerous situations. Characteristic Behavior: Expresses thoughts and feelings with a unique way of speaking. Speaks kindly to and encourages friends. Relationships: A precious friend to Chiikawa and Usagi who cherishes and looks after them. Relationship with Rakko: Respects Rakko as a highly skilled monster hunter and calls him Master.

Those who secretly ate mermaid meat. One day, when Leaf Two was severely injured by the Siren, Leaf One believed the legend and fed them mermaid meat, keeping it a secret from everyone.