This book traces a coherent arc from foundational questions of competition law and economics to the design, measurement, and governance of policy in technology-intensive markets. Part I (Chaps. 1 and 2 ) establishes the intellectual ground. Chapter 1 situates Japanese competition law within comparative legal–economic debates, arguing that the long shadow of deregulatory reform and technological change has widened market power without clear, durable gains in consumer welfare, and contends that credible policy must be re-anchored in empirical industrial organization. Chapter 2 then sets out a methodology to evaluate high-tech regulation through the lens of legitimacy—articulating necessary conditions (sociological acceptance, minimal moral legality, confidence under uncertainty) and sufficient conditions (resources, reflection, expertise, cognition, results) and showing how these criteria discipline regulatory design beyond abstract principle.