noun
mattress; mattress pad (under a futon)
Refers to a Western-style mattress or a thin pad placed under a futon for cushioning or moisture protection.
新しいマットレスを買ったら、腰の痛みが楽になった。
After I bought a new mattress, my back pain got better.
布団の下に敷
I'm looking for a mattress pad to put under the futon.