Traditional thought fused with modern science when Hiroshima’s nuclear annihilation on August 6, 1945, proved the interdependence of space and time. Since the war, Japanese architects have probed the relativity of spacetime through critical debates, pivotal theories, and consequential buildings. The Hypospace of Japanese Architecture pushes past clichés of an exotic Japan to confront the modernity of an island nation whose habit of importing foreign ideas is less about assimilation than transformation, less a process of indigenisation than one of cultural invention. The realisation that buildings are dynamic events — phenomena of space-in-time, not inert objects outside time — continues to inform Japanese architecture and suggests how we can rethink the history, theory, and practice of architecture more generally.