Oshiri Tantei is a detective with facial features resembling human buttocks, marked by prominent rosy cheeks that reflect his name and concept. He consistently wears a signature beret inherited from his father, Oshiri Dandy, maintaining a neatly groomed side parting beneath it. As a polite and meticulous investigator, he solves mysteries through formal deductive methods, citing an IQ of 1,104—a numerical play on the Japanese phrase "ii oshiri" (good butt). His investigations feature recurring catchphrases like "Hmm, I smell a case..." and "Pardon me while I 'poot' you in your place."

His primary companion is Brown, a small anthropomorphic dog with brown fur who accompanies him on cases and often endures collateral effects from Oshiri Tantei’s distinctive subduing method: targeted flatulence to overwhelm antagonists. Their dynamic anchors most investigations. Other recurring figures include Police Chief Maltese, an authority receiving case reports, and the rival Kaito U (Phantom Thief U), who creates adversarial challenges. Oshiri Tantei occasionally involves audience participation to solve puzzles.

In the film "Curry Naru Jiken," he investigates the disappearance of a precious spice called "Maboroshi no Spice," owned by Mr. Paot, starting at their regular café "Lucky Cat" and expanding across town. Beyond detective work, he favors consuming sweet potatoes, noted for digestive benefits, during downtime. Originating from children’s picture books, he helped young readers learn Japanese language fundamentals alongside mystery-solving concepts. His father, Oshiri Dandy, established the beret legacy and gentlemanly demeanor central to the character.