Primarily examined in this article are the "Korean Residents Union in Japan,"which is usually referred to as "Mindan," and the "General Association of Korean Residents in Japan," which is generally called as "Chong'ryeon."Examination of these two organizations, which represent the Koreans now living in Japan, would hopefully reveal what kind of tragic qualities caused by the division of the Korean peninsula have been reflected in the actions of these two bodies. The Koreans in Japan chose to consider either South or North Korea as their homeland, and generally showed a strong Nationalist stance. In other words, they shared their clinging to Nationalism, but they also pursued different states. Such unique situation served to maintain the 'Ideology of Division' among the Korean residents in Japan. The Koreans in Japan have been divided, because the Korean peninsula has been divided. The division between South and North Koreas was directly reflected in the inner dynamics of the Japan-based Korean communities. When governments were installed separately in the peninsula's South and North in 1948, and during the Korean war that broke out in 1950, and also during the subsequent Cold war period, South and North Koreas continued to quarrel with each other, and "Mindan" and "Chong'ryeon" became another active front of that conflict, where people who supported either the South or North continued to fight with each other. Then again, during the time of the April 19th Democratic Movement, the South and North Joint announcement on July 4th,dissolution of the Cold war, and the two recent South & North Presidential Summits, the Korean communities in Japan also displayed some level of harmony and strong unity, with the intention to bind all Koreans in Japan. We can see that not only the hatred and division between the two Korean governments, but also the people's general efforts for reconciliation and exchanges, were all reflected in the actions of the Japan-based Korean communities. Yet the Korean communities in Japan have also been receiving strong influences from the Japanese society as well, and such collective influence accumulated for a prolonged period of time caused some serious changes to occur inside the Japan-based Korean communities which have reached their fourth and even fifth generations since their installation in Japan. The newborn Koreans are distancing themselves from Nationalism, and are also trying to escape the boundaries and walls of ideology. And due to the ever-present discriminative attitude of the Japanese society, the fragmentation of the Korean communities is now more than evident. The Koreans in Japan wish to maintain their dignity and pride as Koreans in foreign countries, so they are trying to contribute to the resolution of the Korean division, and bring all Koreans in Japan together.