In April 2010, a group of migrant members left the National Union of General Workers Tokyo Nambu (Nambu) to join a new trade union called the Zenkoku Ippan Tokyo General Union (Tozen). For a long time, Nambu had a sizable number of mainly English-speaking migrants who worked as language instructors in Tokyo and its vicinity. They formed a group called the Nambu Foreign Workers Caucus (Nambu FWC) as part of the Nambu union in 2004, and have played an active part in migrant activism since then. Despite their visible presence, migrant members remained relatively distant from Japanese members. Around 2010, the distance between the two turned into visible tensions. Some FWC members left Nambu to build a new union, Tozen, which was soon joined by the majority of former FWC members. Their decision to leave Nambu was prompted by a sense of exclusion that arose from the denial of their right to speak in the union. Migrant workers at Nambu had become increasingly dissatisfied, because for them, the union appeared undemocratic and secretive.

The migrant workers’ split from Nambu suggests one way in which linguistic differences can orient the community-making process. Nambu consists of predominantly Japanese-speaking members. At its peak, it had about 500 migrant members out of about 2,500 (Takasu, 2003: 36, 38). To overcome language barriers among its members, the union took some measures to develop a sense of solidarity. Despite its efforts, it ultimately failed to provide an environment where migrant members felt included in union management. Not being able to speak Japanese, migrant members of the union perceived their inability to communicate in their own language as not simply a question of linguistic differences but of who had the right to speak in the union.

It could be argued that the dispute between Nambu and the FWC stemmed from the strained relationship between rank-and-file union members and union organisers. As Turner's study (1995) on Japanese trade unions suggests, the development of a democratically run trade union is a perennial challenge to any union. In the case of the two Japaneseonly trade unions that Turner studied, albeit in different ways, union leaders alone decided the goals and strategies.