It’s a shop dealing in cotton. People in Japan used to buy materials such as cotton and fabrics, and make a futon or zabuton at home by themselves in the past.  The shops selling cotton were called wataya during the period. Not only selling brand new cotton but also offering uchi-naoshi service which make the old cotton brought by customers return to the original elastic state was their job. With the postwar growth of Japan’s economy, most of wataya turned into futon shops.