[Sangetsu]

I would simply replace the tatami mats with new ones. I love the smell of fresh tatami mats, but not the old ones; they tend to absorb cooking odors, dust, and other scents, and then radiate these smells. I also like to clean all wood surfaces with a citrus-based wood cleaning solution.

Due to the humidity and temperature differences between the cold and warm seasons, mold and fungus are big problems. If you don't air out your futons and tatami mats regularly, mold will grow, and the smell is unmistakeable (it is one of the more common odors in Japan). Dessicants in closets and cabinets will help prevent mold, and using bleach on your bedclothes (sheets, pillowcases) will help prevent your futon fro getting moldy, as well as keeping them bright.