International collaboration on complex plasmas research is described. Our collaboration partners are mainly Max-Planck Institute for Extraterrestrial Physics (MPE) in Germany and Joint Institute for High Temperatures (JIHT), Russian Academy of Sciences in Russia. The current target of this collaboration is to approach the critical point in charged systems based on the Totsuji model using an apparatus on orbit named PK-3 Plus, though the research agreement of this collaboration covers much wider research fields. The historical development of this collaboration and our future plans are also described in this paper.
