Simplify the following text for a Grade 7 native English-speaking person.
Original: A futon is a flat mattress with a fabric exterior stuffed with cotton , wool , or synthetic batting that makes up a Japanese bed . Futons are sold in Japan at speciality stores called futon ` ya as well as at department stores .
Simplified: Futons are generally used with a futon cover , because these make it easy to keep the futon clean .