A red ogre. His name comes from being a crybaby (naki-mushi) as a child. He hates humans because they killed his mother 200 years ago; consequently, he has closed off his heart and acts violently toward those around him, making him disliked by other monsters. He is allowed to stay on the island only through Gunjo's mediation. He has the ability to jump incredible distances by powering up his legs. Though he appears boorish, he is naturally kind. He has a large build but is slightly shorter than Gunjo. First person: I (rough, regional). He has a scar on his mouth from a human arrow shot when he was a child. He's the type to burst into laughter at funny faces. He lives in a treehouse. He is childhood friends with Gunjo. Speech style: blunt and commanding ("...right?", "...isn't it?", "Do ...!"). His favorite food is Heavenly Maiden Mushrooms.

A blue ogre. He was separated from his mother 200 years ago due to humans, and her whereabouts remain unknown. He has a long history with Naki; they have great coordination and are best friends. He is a smooth talker with a bit of a devious streak, but gets along well with other monsters. He is a bit soft on Kotake. He has the ability to turn invisible. He is slim and tall, with a kind and cheerful personality. First person: I (casual). He is Naki's childhood friend. Speech style: friendly and casual ("...right?", "...yeah!", "...isn't it?"). His favorite food is Heavenly Maiden Mushrooms.

A human baby boy who wandered onto Monster Island and became friends with Naki and the others. He can speak a little, saying things like "Yummy!", "Peek-a-boo!", and "Yeah!". He has a topknot hairstyle. He is incredibly small and cute with big, round eyes. He loves playing pranks. He has an older brother and a sick mother.

A bitter melon (goya) monster. He is about the same size as Kotake. He lives next door to Naki. His house is frequently destroyed by freak accidents (poor guy), at which point he always screams "Why me?!" He often suffers from bouts of bad luck.

A cat monster. An older-sister type character. She has two tails that she can move like arms. First person: I (feminine/casual). Second person: you (blunt) or by name without honorifics.

A monster that is a mix of a catfish and a mushroom. He has blue-green skin and a sleepy-looking face. He pushes the responsibility of looking after Kotake onto Naki and Gunjo. He gives harsh punishments to those who break the laws (such as hanging them from a cliff). He is the elder of Monster Island. His speech style is like an old man. He fears that humans will attack the island. He orders Naki and the others to capture the human child Kotake and use him as a "hostage" to protect the island. He is the one who keeps the island together.