We designed an ambient LED signage display that “mimics ductwork.” The LED signage is modeled after ducts installed on the ceilings inside actual buildings, and has been designed as cylinders and rectangular prisms that are the same size as real ducts. It represents a new form of LED signage that coexists with architecture. The economic information displayed on the LED signage is updated in real time every day with economic data from SPEEDA and NewsPicks provided by Uzabase. It was conceived as a scene in which the information flows through the ducts together with water, racing through the city of Marunouchi, one of the centers of the Japanese economy. To mimic ductwork, we simulated how sunlight enters over the course of a year. In addition, by installing illuminance sensors and linking the display to the lighting in the interior space, we designed the visuals on the LED signage to be overlaid with shadows. By reflecting color from elements such as the staircase, we pursued “mimicry” as closely as possible.