Japan's master narrative of national homogeneity tends to deny the existence of Ainu people as an ethnic minority group. Today many people think Hokkaido island has been an integral part of Japan since ancient times, but before the modern notion of boundaries emerged, Ezochi (present-day Hokkaido), or Ainu land, was considered to be foreign barbarian territoy outside Japan. This book explores historically the northern frontier of the Japanese state in the pre-Meiji times and looks at the process how the China-centered worldview was replaced by the modern notion of boundaries in late Tokugawa Japan. Focus is placed on the Tokugawa intellectuals' perceptions of Ezochi and the northern boundaries, as the author believes the changing notions of borders became the driving force behind the incorporation of Ainu land into inner Japan. This book also examines the social, economic, and external conditions surrounding Ezochi at the time, which turned the Tokugawa elite's attention to the northern island. Thus, this book provides insightful and useful information for students and scholars who are interested in the Ainu and Japanese history.