A mysterious sommelier known only as Killer-san operates out of a hidden wine bar on Killer Street. Though he never leaves the bar, he solves baffling crimes by applying his deep knowledge of wine to the clues brought to him. The young weekly magazine journalist Akane Maki becomes his regular partner after she stumbles into the bar while investigating a locked‑room murder she witnessed. Describing the scene to the sommelier, she receives unexpected hints that lead to the solution, and a working relationship is born. Akane continues to bring new cases to Killer‑san, each more puzzling than the last.

The setting revolves around the intimate, almost secret wine bar on Killer Street, where the sommelier listens to accounts of crimes and uses analogies drawn from wine regions, vintages, and tasting notes to illuminate hidden truths. Akane, a determined and sharp‑witted reporter, provides the legwork while the sommelier supplies the deductive spark from his armchair.

Notable narrative arcs include the initial locked‑room murder that draws Akane into the bar; a fatal incident on a rain‑soaked highway where the details of the crash strike Akane as suspicious; a bizarre death scene in which a man lies dead before a full French course meal; a case hinging on the testimony of a blind witness who claims the killer smelled of a wine from the Vosne‑Romanée village; a murder inside a reputedly haunted apartment complex where the only clue is two sounds heard in the night; and a high‑profile killing of an elderly woman in an upscale residential district. In each arc, Killer‑san guides Akane toward the truth without leaving his bar, his reasoning often starting from a single glass of wine or a characteristic of a particular grape.