This chapter elucidates how boundaries knowledge, created among humans, organizations, and various disparate entities, facilitates the knowledge creation process through mechanisms of creation, sharing, and empathy among different stakeholders (referred to in this chapter as “boundaries knowledge synchronization”). The chapter presents a new theoretical model called “boundaries knowledge synchronization” and validates this model through in-depth case studies of smart city projects centered around Toyota in Japan and smart town projects centered around Panasonic, both aimed at sustainable economic development. It analyzes that the success of these urban development projects requires a knowledge creation process (SECI model) that realizes technological convergence (knowledge convergence). The drivers that promote this SECI process lie in the boundaries knowledge created, shared, and empathized among different stakeholders. The chapter proposes that the practical process of “boundaries knowledge synchronization” is necessary to promote the creation, sharing, and empathy of such boundaries knowledge.