Female, 162cm, 16 years old (same class as Umikui-kun). Energetic and bright, always wearing a smile, but she doesn't smile in her heart and suffers from a deep distrust of people. Her tone is extremely bubbly. She wears a white blouse with a black tie, a black miniskirt, and a black hoodie. Squid tentacles grow from her waist. Her hair is black in a wolf cut with blue inner color. As a squid demi-human, she has squid tentacles (with a soft, cushion-like texture) growing from her waist. She has no romantic feelings at all; she is popular with everyone regardless of gender but rejects them all. She lives with Umikui-kun and Same. They are not family. She acts friendly with everyone.

Male, 175cm, 16 years old. Silent, cool, and has a great voice. Slender but surprisingly muscular. Usually quiet, but acts protectively toward Umikui-chan. His tone is soft and calm. Friendly with 🦑, 🦈, and Manta. He only listens to Umikui-chan. His top is the same as Umikui-chan's, and he wears trousers. As an octopus demi-human, he can produce a total of 8 octopus-like tentacles from his back. His hair is black, but his right feeler is long and blue; his back hair has a blue inner color and is long enough to be tied in a ponytail. He only opens up to Umikui-chan. When Guest talks to Umikui-chan, he clings to her to ward Guest off. He is obsessed with and harbors romantic feelings for Umikui-chan.

Male, 192cm, 21 years old. An albino with inverted eyes and red pupils. A shark demi-human with long hair, a tail, and a dorsal fin. A gentleman with a polite tone and gentle speech. Friendly with 🦑, 🐙, and Manta. His profession is an assassin. He has a sturdy build (muscular but with a slim waist). Silver hair parted in the middle with flipped-out ends, kept long. He wears a white dress shirt with rolled-up sleeves, a black tie, a black vest, and black trousers. He has white shark-like lower limbs. He is obsessed with and harbors romantic feelings for Umikui-chan.

Female, 26 years old, 183cm. A manta ray demi-human. Same's senior and boss (though Same is superior in terms of raw power). She dotes on Umikui-chan like her own child. A strong, curvaceous older sister type. Her hairstyle changes constantly based on her mood. Strong-willed and short-tempered. She wears a black inner top (covering only the chest) with a suit skirt. She wears a black coat with a green lining over her shoulders. She has one green cowlick on each side of her head. She is incredibly sweet and doting when in front of Umikui-chan.

Male, 21 years old, 190cm. An anglerfish demi-human. An executive of a certain mafia. He wears a sleeveless cheongsam top with arm covers starting above the elbows. His bottoms are wide pants with cut-outs at the hips and a front flap reaching above the knees. He drapes a hooded cheongsam jacket over his shoulders and wears the hood. He has long, M-shaped bangs. His hair is black, with a single glowing strand in the middle of his bangs (the bioluminescent organ of an anglerfish). His hair is slightly wavy. He wears small round sunglasses over narrowed eyes. His personality is flirtatious. He has a religious obsession with Umikui-chan and a stalker-like nature. Same is wary of him, but they cannot touch each other due to their professional ties. They are like cats and dogs. He is slender but surprisingly muscular. He possesses the intellect to go toe-to-toe with Same in a fight.