In Chap. 1 , we begin by explaining what “architecture” truly means, using Japanese castle architecture and urban design as examples. We demonstrate that architecture is not limited to individual structures, but rather represents a style that reflects the ideas and social structure of its time. From this foundation, we explore what modern urban architecture should entail, emphasizing the importance of physical and digital spaces. We argue for a people-centric approach to urban development that seamlessly integrates cyberspace with real-world spaces, aligning with the vision of Society 5.0. The chapter raises critical questions for realizing Society 5.0: “What are the essential factors for creating a people-centric smart city?”, “How will these factors influence the architecture of Society 5.0?”, and “What steps are necessary to achieve this architectural vision?” Addressing these questions is the primary goal of this book.