Postwar Japan was ravaged by poverty and desolation as a result of various factors. It lost much of its colonial holdings overseas, which led to a sudden and massive disruption of industry (in particular agriculture, as noted by John W. Dower), along with many other reasons, the most obvious being the occupation by US forces. Groups such as several Japanese people, the zainichi community, and the Okinawans all employed their own mechanisms of mutual aid to assist each other in a quite literal struggle to survive following WWII.
Japanese workers for Yomiuri in the postwar era employed a most definite form of mutual aid in a manner most comparable to that of a labor union’s: when faced with inequity in their employment and difficulty in their ability to survive, they took over the production of the newspaper, thus cutting the owner of Yomiuri out. This allowed them to continue with their work without the government’s intervention (as they were not formally on strike, which would have drawn quite some attention), and maintain their rights as workers. Of course, this form of mutual aid is still relevant in contemporary times: for instance, the bookstore and general store, or food co-op at the Student Center in UCSD are student-run. Labor unions of course are also a way to offer a way to fight for rights to workers.
The zainichi communities were of course also affected by this postwar struggle, with organized communities seen in the breweries or pig farmers of Kang’s memoirs. There was also the mutual aid collective known as the Chongryon, which provided all sorts of services and functioned similarly to a government might have — most notably providing education for many Koreans in Japan. These sorts of communities of course still exist today, although the Mindan has largely supplanted the Chongryon in popularity. These communities continue to support Zainichi Koreans who remain in Japan, with the Mindan notably providing support during the Tohoku earthquake.
We also see a particularly interesting form of mutual aid in the story of Fujiki Hayato, who tells stories that keep the culture and history of Okinawa alive, especially in regards to its unique oppression by both Japan and the United States. I distinctly remember us discussing the ways we see storytelling as a special subversive way of perpetuating culture, in a similar fashion to that of American Indigenous oral traditions, and so forth. Fujiki Hayato serves as an interesting example as we must also remember that mutual aid is not entirely material — for instance, even the Korean organizations (in particular Chongryon) teach in Korean and teach Korean culture in order to maintain the community.