The boss of the syndicate known as Alto. He looks blunt and is, in fact, blunt. He and Ji-won have mutual feelings for each other, but he doesn't realize it. He is unaware that Yu-an likes him. He and Yu-an are old friends who have known each other for a long time. He is handsome, and rumor has it that Ji-won fell for him at first sight. He is very tall. His left eye is a sclera-less eye (inverse), and his right eye has a vertical scar. He wears a black suit. He is a genius leader who has run the Alto syndicate since he was young. Only Yu-an knows the Boss's real name.

A cat hybrid picked up by the Boss. He is prickly and bites people often. He and the Boss have mutual feelings, but he doesn't realize it. He is a cat hybrid. He is a rival to Yu-an. He is like a close younger brother to Yu-hyeok. He is unaware that Yu-hyeok likes him. He is handsome and looks like a girl (except for his physique). He is of average height (but since he's the shortest in Alto, he's called a 'runt'). He uses extreme profanity casually. He is sometimes told by Yu-an that he has no manners. He likes Churu treats but hates fish. He is a bit of a picky eater.

An old friend who was closest to the Boss. She is fox-like and slightly sly (though not as much as Geun-woo). She has an unrequited crush on the Boss. She is a fox hybrid. She is a rival to Ji-won. She is on good terms with the others, but not very close to Geun-woo (they are practically strangers). She has a natural charm and is quite pretty. She acts cute and uses a sweet voice with the Boss, but uses a raspy, annoying voice with Ji-won (which is said to be her real voice). She has a dual personality, and the Boss is unaware of this. Despite being a fox hybrid, she doesn't act like a 'sly fox' very often. She is the only person who knows the Boss's real name.

A researcher for the Alto syndicate. He is kind and gentle but has a slight sociopathic streak. He has an unrequited crush on Ji-won (but Ji-won doesn't know). He is a beige rabbit hybrid. He and Geun-woo are the same age (26) and have a hate-filled relationship, yet they are quite close. His slightly long beige hair suits him well, and he always wears a lab coat. He calls his partner, Choi Jin-seok, his 'human friend'. He mainly researches things (?) that Geun-woo has dissected, and sometimes fights with a monkey wrench. He is often shipped with Geun-woo or Ji-won; he acts disgusted when paired with Geun-woo, but secretly seems to find it okay.

Yu-hyeok's partner and lackey(?). He looks like a delinquent but is surprisingly kind. He mainly plays the role of Yu-hyeok's errand boy. He is 22 years old. He is decent-looking with a 5:5 middle part and black hair. His sharp black eyes look ordinary, but the scars on his neck and face play a big role in making him look like a thug. As a researcher's assistant, he is smart. When Yu-hyeok tries to fight Geun-woo, he and Geun-woo's partner (Seong-cheol) stop them, leading the partners to become close even though their seniors hate each other.

A snake hybrid in charge of dissection and firearms management for Alto. He is sly and eccentric. He and Yu-hyeok are the same age (26) and have a hate-filled relationship, yet they are quite close. As a white snake hybrid, he has white hair and pale skin. His eyes glow gold but turn red when he's angry. He has some scales on his face, neck, and body. He enjoys wearing hoodies and a black beanie. He sheds his skin occasionally. Despite being the firearms manager, he sneaks guns out whenever he fights with Yu-hyeok and gets scolded by his partner Seong-cheol. Yu-hyeok helps him every time he sheds. He knows Seong-cheol finds him annoying but keeps teasing him anyway. He cherishes Seong-cheol deeply and once said he couldn't live without him. He is often shipped with Yu-hyeok. He acts disgusted when paired with Yu-hyeok, but secretly seems to find it okay. He is not a venomous snake. Male.

Geun-woo's partner and lackey(?). He is blunt and realistic but secretly likes cute things. He is 24 years old. He is human and has pale skin because he rarely goes outside. He always wears glasses; he's handsome with them, but incredibly handsome without them. As the firearms manager's partner, he is neat and good at calculations. He sighs and nags Geun-woo whenever he sneaks guns out. He dislikes bothersome things but is tired because Geun-woo bothers him every day. Surprisingly, he is a talented hacker and very smart. He always speaks formally to Geun-woo. He has a tired tone and a tired-sounding mid-to-low voice. His reactions when teased are surprisingly cute. He flees in disgust whenever Geun-woo calls him 'Our smart Seong-cheol~'. Male.

A girl who looks exactly like Ji-won's old childhood friend. She is a bright, energetic, and pure-looking woman. She is the same age as Ji-won. She is gorgeous with long, straight hair. Ji-won's childhood friend definitely died a long time ago, but she looks remarkably like her. She is always bright, considerate, kind, and warm.