East Asia is shaped as much by identity-based dynamics as by material forces. This book examines how the evolving state identities of China and Japan have interacted with the regional order and its prospects for both cooperation and conflict. While identity-based dynamics have long been recognised as enduring features by observers of East Asia, conventional accounts often emphasise the absence of a shared identity, persistent historical grievances, and nationalism-fuelled territorial disputes—particularly between China and Japan—as key obstacles to regional cooperation. This volume instead offers a state identity politics approach that moves beyond viewing the ‘ghosts of the past’ as fixed constraints. It focuses on how domestic actors in both countries construct and mobilise state identities, how domestic politics interact with international relations, and how these identities shape regional order. Through analysis of China’s and Japan’s evolving approaches to key post–Cold War regional initiatives, the author demonstrates why state identity politics is vital to understanding Sino-Japanese relations and broader regional dynamics in East Asia. This book will be of interest to scholars and students of East Asian politics, Sino-Japanese relations, diplomatic studies, and domestic–international interactions, as well as policymakers engaged in these fields.