"Holmes Agency” is a private detective office known as the ";Big-Eating” Detective Office. Seiya Takano, who is known for have a huge appetite, gets assigned to this office as the new leader. Ryosuke Noda and Ryoko Izumi, both also having a big appetite work under Seiya. Murder, robbery, and kidnapping - many incidents occur around them. And the three solve each of the many cases in a most surprising way - their appetite results in marvelous speculations! They eat at themurder scene. They eat on the track. They even eat dog food! They keep on eating and eating, not even listening to the witness. Everywhere they go, they eat and eat and eat! And every time after finishing, the criminal appears. KUITAN is the words "Big-Eating” and Detective combined together. "Real Gourmet” plus "Real Mystery”. The big-eating detectives are on the run, solving cases from their deep knowledge about food.

Ajiyoshi Yoichi is a culinary prodigy who manages the eating house together with his mother. One day, Murata Genjiro appears in the eating house and is surprised at the delicious taste and delicate culinary skills of the katsu-don prepared by Youichi. Subsequently, Youichi is being invited to the Aji-oh Building in which he is involved in a spaghetti match with the in-house Italian chef, Marui. Youichi's novel culinary ideas, coupled with his enthusiasm of serving the best for his guests, allow him to defeat Marui in the match. From then on, Youichi begins to compete with other rivals in the race for the best tastes and dishes.