The Holmes Agency is a private detective agency nicknamed the Big-Eating Detective Office. Seiya Takano, who is known for have a huge appetite, becomes this office's new leader, after working on his own in the same field. Ryosuke Noda and Ryoko Izumi work under him, both also having a big appetite.

Murder, robbery, and kidnapping-the three solve each of many such cases in a most surprising way: their appetite results in marvelous speculations, deductions, and conclusions!

They eat at the murder scene. They eat on the track. They even eat dog food! They keep on eating and eating, focusing on the food to the exasperation of the police and witnesses. And every time after they finish all the food in sight, they finish off the criminal, too.