natto ( (hiragana), 納豆 (kanji); "nattō" or "nattou") is a traditional japanese food made by fermenting soybeans. natto is known for its strong musty smell and unusual slimy texture, which yields mucous-like (or sticky) strings when stirred and eaten. in order to mediate some of the strong flavors, it is usually eaten on top of rice with , a soy sauce-based condiment, or japanese mustard to their liking. eating natto as a custom is not so popular in kansai area. whether it is popular or not depends on regions in japan.