It’s a Japanese-style mosquito net which is hooked at the upper four corners of a room. The traditional Japanese houses were gappy and the windows were often left open during sleep in summer, so this was the must-have item. So kaya was one of the martial packages from the Edo era to the Showa era. The Japanese-made mosquito nets have been recently assessed as useful and often used for the prevention of diseases such as Dengue fever in subtropical regions and Africa.