Shirasu is the area covered with white pebbles between the Noh stage and the auditorium. Until the Edo Period, Noh stages were set up under the open sky and the auditorium was in a separate building, with a wide space covered in pebbles between them. This space added grandeur to the stage, while the white pebbles reflected sunlight onto it. Since the Meiji era, Noh stages and auditoriums are usually located in the same building. The pebbled area is kept narrow, but remains as a reminder of the days when Noh was performed under the sky.