Most households in Japan are a member of their neighborhood association (NHA). Japanese NHAs function as basic organizational building blocks that promote a sense of security and familiarity at the local level and facilitate the general organizational efficiency of Japanese society. In this empirically oriented paper, new information is provided with regard to the organizational structure, activities, autonomy, and social meaning of four NHAs in Hiroshima City. Simply by existing and visibly performing all kinds of functions, such as cleaning the neighborhood or patrolling the local area, Japanese NHAs can be viewed as a kind of social lubricant that increases the overall societal efficiency in Japan.