North Korea is still a strictly secluded state and little is known of its past and present though recent research using documents from countries in the former Soviet bloc has produced a number of breakthroughs especially in the discussion of the origins of the Korean War. Among others, history of relations between North Korea and Japan is most unexplored. One might assume that North Korea has had little interest in developing relations with Japan because of the adversary political ideologies between them. Focusing on the early history of North Korea, the present paper demonstrates that this assumption is quite wrong. North Korea needed the Japanese industrial products and technical know-how from the start of its state formation. This gave its leader, Kim Il-sung a good economic reason for establishing official relations with Japan. However, in the early period, he had little political power to execute his own policy toward Japan. His action had to follow the Soviet grand strategy toward the West. By 1961 he achieved a great success in his attempts. This afforded him a promising prospect for the military built-up using Japanese products, that is, developments of the nuclear and missile programs in the later periods.