Japan’s relations with Korea have been quite complicated. The complication is product of both events on the Korean peninsula such as division of Korea, the Korean War and legitimacy contests between North and South Korea as well as changing inter-state equations in the region. In the given context, it is understandable that Japan has been contesting with North Korea which got aligned with the USSR and China after its very inception. But it is difficult to understand the contest of Japan with South Korea as both the countries share common friend in the US and common concerns in the form of China and North Korea. Actually, Japan and South Korea are both vibrant liberal democracies and their economic development models have also been quite similar. Japan and South Korea also have huge cultural and educational exchanges in past few decades. The contests of Japan with a foe (North Korea) and a friend (South Korea) are seemingly located in their colonial history, identity issue and territorial disagreements. On most of these issues, North and South Korea both find difficult to agree with Japan. With the emergence of Japan’s quest to become ‘normal’ power and changing inter-state relations in East Asia, North and South Korea both got alarmed because of their past historical experiences. An aggressive Japan is considered unacceptable and the most imminent threat for Korea as well as the region. In the above context, the paper seeks to explore the nature, trajectory and cause of Japan’s contests with North and South Korea.