On 22 February 2003 a group of foreign residents of Japan gathered in Yokohama's Nishi Ward next to the Katabira River to protest the awarding of a residency certificate (juminhyo) to a seal called Tama-chan. Tama-chan had frequented the river and as such was awarded the certificate because he was "more or less like a fellow resident." The group of foreign residents criticized what they believed to be discrimination by the Japanese state because, whilst a seal is able to gain a residency certificate, foreign residents are legislatively excluded from obtaining one. The Tama-chan protest provides an opportunity for investigating not only the residency registration system, but also other population registries such as the Japanese family registration system and alien registration system. The author of this article argues that a deeper and more informed understanding of the processes of marginalization of foreign residents in Japan can be achieved through a comprehensive investigation of Japan's population registries and their respective histories. The author explains how these population registries are sites of tension in which contained notions of Japanese citizenship and national identity are being contested by foreign resident populations with vested interests in Japan as home, thus revealing the inadequacies, inconsistencies, and ambiguities of these registration systems.