A polite and meticulous super sleuth known as the Butt Detective operates in a world where his face is a literal pair of buttocks, complete with pronounced cheeks and a central cleft. This unusual appearance is treated with complete neutrality as he runs his detective agency, solving a seemingly endless stream of baffling mysteries. His approach to crime-solving is marked by an intellectual rigor, starting with his signature catchphrase, Hmm, I smell a case, and concluding with a unique and effective method of subduing criminals. After declaring Pardon me while I poot you in your place, he deploys a powerful blast of flatulence from his face to incapacitate the culprit.

The detective is rarely alone, accompanied by his faithful but often unfortunate canine assistant, Brown. Brown is a small, talkative dog who serves as the detective’s loyal aide, though he frequently finds himself on the receiving end of his partner’s digestive-based attacks. The series is set in a vibrant, pastel-colored town populated by anthropomorphic animals and other quirky characters. The local police force, the汪汪警察局 (Wanwan Keisatsujo, or Bowwow Police Station), is led by the diminutive but earnest Chief Maltese, a white Maltese dog who regularly seeks the Butt Detective’s expertise. The officers, including the competitive Detective Pointed-Ear and the joke-telling Detective Perm, provide both comic relief and procedural support.

The overarching narrative introduces the detective’s primary rival, the enigmatic Phantom Thief U (Kaito U). A master of disguise with a flamboyant sense of style and a strict code of thieving ethics, Kaito U delights in sending advance notices of his heists, turning their encounters into elaborate games of wits. These confrontations form a recurring backbone of the series, with the thief frequently targeting treasures like the Goddess Scarf or the starry sky jewel while the detective works to protect them.

Several notable narrative arcs expand beyond the standard episodic cases. One major film storyline pits the Butt Detective against his most formidable adversary yet, a villainous genius named Shiriarty, in a plot involving a mysterious treasure known as the O-PARTS that threatens to plunge the world into darkness. This case forces him to collaborate with an investigator from the international police organization Wanterpol. Another significant arc involves the Kaitō Academy, an international crime syndicate. To investigate a disappearance linked to an idol contest on Stardust Island, the Butt Detective goes undercover as an idol, forming a temporary and uneasy alliance with his nemesis, Phantom Thief U, to recover the valuable Moonlight Stone and thwart a secret conspiracy called the Dark Age Plan. This storyline also delves into previously unknown details about his assistant Brown's past. Another key case reveals his backstory with a former partner, Suisen, as they investigate an art forgery ring at a Metropolitan Museum, an investigation that leads to the detective sustaining a severe injury. The series also introduces his father, Oshiri Dandy, a fellow detective who bequeathed him his signature beret.