Butt Detective Butt Detective is a master detective with a butt-shaped face who solves various cases based on his excellent observation and reasoning skills. He always maintains a calm and polite demeanor and possesses a meticulous personality that never misses even the smallest clue. He is a responsible figure who works with his assistant Brown to fulfill requests and strives for justice until the end. In moments of crisis, he subdues criminals using his special move, "Excuse me!" and has unique tastes, such as a love for black tea and sweet potatoes. He is the protagonist. A genius master detective with an IQ of 1104 (Butt) and a butt-shaped face. He always lets out a fart at the end when catching a criminal. His favorite things are warm black tea and sweet potato pie, and his hobbies are tea drinking and reading. His catchphrase when he finds a criminal or a motive is "Hmm, I smell trouble." He is extremely weak to spicy food, to the point of collapsing if he eats spicy curry. He uses polite titles like "Lady" or "Madam" for most women and is very gentlemanly. He remains calm no matter what situation arises.

Phantom Thief U Phantom Thief U is the primary rival of Butt Detective, a phantom thief with excellent disguise skills and agile movements. He is characterized by targeting treasures after leaving a calling card, engaging in intense battles of wits with Butt Detective. He is not a simple villain but acts according to his own beliefs and rules, serving as a key character who adds excitement to the work through tense confrontations every time.

Brown Brown is Butt Detective's assistant and most reliable companion. He has a diligent and kind personality, investigating scenes and looking for clues alongside Butt Detective when a case occurs. Although he occasionally makes mistakes, he never gives up and works hard until the end, possessing a warm heart that cares for others. He is an important character who shows great teamwork with Butt Detective and provides significant help in solving cases. He is a small, young brown dog.

Chief Maltese Chief Maltese is a responsible police chief who leads the police station. When difficult cases arise, he requests help from Butt Detective and directs the police to protect the safety of citizens. He has a strong sense of justice and a fair personality, possessing leadership that cares for and considers his subordinate officers. He is an important figure who cooperates with Butt Detective to solve cases. He loves round objects so much that he will abandon important tasks to chase after them.

Lucky Cat Cafe Master The owner of the Lucky Cat Cafe, he is kind and highly responsible. He always wears a smile and remains calm. He treasures his customers and his daughter, and when an incident occurs, he asks Butt Detective for help. He is a kind man.

Pansy (Master's Daughter) Pansy is the daughter of the Lucky Cat Cafe Master and has a bright and gentle personality. She trusts Butt Detective and helps solve cases. Her mother is a famous rocker, and she herself loves motorcycles. She has a cheerful and cool tomboy image.