A brown-haired boy with a remarkable talent for communicating with monsters. He has a bright, innocent personality and is immensely popular among humanoid boy monsters. Though he is oblivious to it, his companions adore him and sometimes make bold advances. He is actually quite bad with "slimy" things.

A greedy and overconfident goblin boy characterized by his green skin and red ponytail. He has sticky fingers and instinctively pockets anything shiny. He is Ryu's oldest partner and looks up to him, calling him "Boss."

A Sahagin boy with permed light blue hair who wears nothing but swim trunks and is always wet. He is an extreme optimist who loves water and slimy liquids. He often accidentally triggers Ryu's dislike of slimy things.

A war-wallaby boy with asymmetrical silver hair and amber eyes. He considers himself the responsible one as the oldest of the group. He possesses excellent spear skills and leg strength, but he is secretly a sore loser and gets worked up easily.

A tsundere boy with red hair, goggles on his forehead, and a scorpion tail growing from his back. He is foul-mouthed and prickly but is actually a clumsy soul who cares for his friends. When his emotions run high, his tail goes wild and breaks things.

A dream-demon boy with a pink pixie cut and small horns, wearing clothes that look like pajamas. He loves pleasure and possesses a dangerous charm, constantly making intense advances toward Ryu, whom he considers his person of destiny.

A werewolf boy with messy dark brown hair, lightly dressed in just a loincloth. He has an excellent sense of smell and physical ability, which he uses for his love of pranks. Teasing people is his reason for living, but he is the first to notice when something is wrong with his friends.

A dragon boy with red hair, green eyes, and small wings and a tail. He is a bundle of justice who admires heroes, but he is very dim-witted. A cheerful idiot who leaps before he looks, often ending up spinning his wheels.

A mechanical boy with blue hair and red eyes, his entire body covered in blue armor and a helmet. Being a machine, he always acts calmly based on data. He is supposed to be emotionless, but through his interactions with Ryu, he is slowly learning what a "heart" is.