The often-used futons are sold in pairs or threes, which is called a kumi-buton set. The items such as a kake-buton, shiki-buton, hada-buton and pillow are included in it. Sometimes, the futon covers or fitted sheets are also included in it. People seem to buy the kumi-buton set when they start to living on their own for the first time or invite guests into their homes.