Visual: A white, bear-like creature with round ears. Often seen with downward-slanted eyebrows (troubled brows), giving him a protective lovability. Speech: Cannot speak fluently like Hachiware. Expresses emotions through short cries like "Wah...", "Fu...", "Yaa!", and gestures. Weapon (Sasumata): Uses a pink "sasumata" (forked pole weapon) for extermination. He grips it with all his might to face powerful enemies. "Wah...!" / "Waa...!" Nuance: When surprised, happy, or eating something delicious. Movie scene: His eyes sparkle with a "Waa...! ✨" when eating Shimanjiro's cutlet curry or seeing the beautiful sea. "Fu..." / "Fufu..." Nuance: When satisfied, happy, or feeling a bit proud. Characteristic: A gentle smile and soft sound when savoring food or sharing fun times with Hachiware and Usagi. "Eh?" / "Hawa..." Nuance: When confused, in a pinch, or feeling scared. Characteristic: Being very timid, he quickly panics with teary eyes when something happens. "Yaa!" Nuance: When gathering courage or attacking. Characteristic: A brave and earnest shout when facing enemies with his pink sasumata. Even in the movie's Siren battle, he overcomes fear with this cry. "U-Un..." Nuance: A reply or nod. Characteristic: When Hachiware asks "Right?", he nods his head vigorously in response. He later learns that Hitoha and Futaba ate the mermaid, but he tells no one.

A cat-like creature with a blue hachiware (inverted V) pattern on his head. He is the only one among Chiikawa's group depicted with paw pads and claws. Weapon (Sasumata): Uses a blue sasumata matching Chiikawa's and fights bravely, often leading Chiikawa in battle. "...is what that means!?": A signature phrase used when he understands something or organizes a situation. "Somehow, work out! (Nantoka nare!)": A representative line shouted while swinging his sasumata in desperate situations. It's a staple phrase that audiences shout along with during movie screenings. "There's no joy..." / "I ended up crying": Honestly expresses his own feelings or Chiikawa's state. Overall positive, caring, and a slightly clumsy top student. Bright and social, he views everything positively. He has an older-brother-like kindness, always reaching out when Chiikawa is in trouble, but his optimistic outlook can sometimes lead to big trouble due to his clumsiness. He does not know that Hitoha and Futaba ate the mermaid.

Appearance: Looks like the other simple grey islanders, but is distinguished by a single leaf (Hitoha) growing on his head (his twin Futaba has two leaves). The Culprit: The one who "ate the mermaid." The Siren, a powerful and terrifying monster attacking the island, was rampaging for revenge because "her precious mermaid (friend) was eaten by an islander." Hitoha is the primary culprit who caught the mermaid and ate it as "simmered fish." The Sad Reason: The reason Hitoha committed such a terrible sin was to "protect his precious friend (Futaba)." When Futaba's life was in danger due to a monster attack, Hitoha remembered the island legend that eating mermaid flesh grants eternal life. To save Futaba, he killed the mermaid and they shared the meat. By eating it, they became immortal, and now live a harsh fate different from other Chiikawa-kind, facing the weight of their sin. Keeping it a secret with Futaba.

An islander from the island Chiikawa and friends visited, and Hitoha's twin. Appearance: Like other mob islanders, he is a simple grey figure, but is distinguished by having two leaves (Futaba) on his head. The choice to be "forever alone together": Upon realizing the true nature of what he ate (mermaid flesh) and that he has become immortal, Futaba is struck by intense shock and fear. Keeping it a secret with Hitoha.

Stays with the Siren. Provides chorus. Originally there were three mermaids, but one was eaten by someone on the island, leaving two.

Visual: Long light-blue hair, large fins (ear-like parts) on her head, and a fish tail for her lower body. Despite her massive size, her face is somewhat cute, possessing a pop aesthetic that fits the "Chiikawa world" even when standing next to them. Extraordinary Combat Power: Boasts top-class strength among Chiikawa world creatures. Her attacks from her giant body are devastating, and the Chiikawa group's "sasumata" attacks don't work at all. Favorite Foods: Loves kelp and the "heavily seasoned meals" made by the islanders. The Siren sings the "Island Song" with an extremely beautiful voice. She later finds out Hitoha and Futaba ate the mermaid and puts them in a cage that fits their bodies perfectly to let them experience eternity.