The authors attempted to present the state of disputes regarding the delimitation of marine areas based on a discussion of the practices of countries in the East China Sea and the Sea of Japan region. The authors describe the disputes regarding the islands of Senaku (Diaoyu) between both China and Taiwan and Japan and those over the Dokdo (Takeshima) archipelago between the Republic of Korea and Japan. There are many similarities between these two marine territorial disputes. The core of the disputes is land that is devoid of significant economic importance. Due to this, these areas were not previously of interest to coastal countries. They came to the forefront when their location facilitated determining exclusive economic zones. This intensified when evidence of crude oil and natural gas resources was detected in these areas. Tensions eased when geological reports revealed that initial estimates were overly optimistic. The fundamental cause of disputes over archipelagos is that they can be used to determine exclusive economic zones. The problem is compounded when the politicians of Eastern Asia incite historical remembrance. This is especially evident in the cases of Japan, the Republic of Korea, Taiwan, and China, whose governments are, to some extent, hostages of ultra-nationalistic factions.