Reimagining Kyokai: Layered Permeability in Yoshiji Takehara’s Modern Residences

Traditional Japanese architecture is known for its open, ambiguous spatial boundaries (“kyokai”), which integrate nature and dwelling through Zen/Shinto philosophies. Yet modern urban housing, driven by high-density minimalism, flattens spatial hierarchies and erodes these rich boundary concepts. This study aims to explore how Japanese architect Yoshiji Takehara reinterprets traditional spatial principles to reconstruct the interior–exterior relationships in modern housing through a mixed-methods approach—including a literature review, case studies, and semi-structured interviews—verifying the hypothesis that he achieves the modern translation of traditional “kyokai” through strategies of boundary expansion and ambiguity. Analyzing 78 independent residential projects by Takehara and incorporating his interview texts, the research employs spatial typology and statistical methods to quantify the characteristics of boundary configurations, such as building contour morphology, opening orientations, and transitional space types, to reveal the internal logic of his design strategies. This study identifies two core strategies through which Takehara redefines spatial boundaries: firstly, clustered building layouts, multi-directional openings, and visual connections between courtyards and private functional spaces extend interface areas, enhancing interactions between nature and daily life; secondly, in-between spaces like corridors and doma (earthen-floored transitional zones), double-layered fixtures, and floor-level variations blur physical and psychological boundaries, creating multilayered permeability. Case studies demonstrate that his designs not only inherit traditional elements such as indented plans and semi-outdoor buffers but also revitalize the essence of “dwelling” through contemporary expressions, achieving dynamic visual experiences and poetic inhabitation within limited sites via complex boundary configurations and fluid thresholds. This research provides reusable boundary design strategies for high-density urban housing, such as multi-directional openings and buffer space typologies, and fills a research gap in the systematic translation of traditional “kyokai” theory into modern architecture, offering new insights for reconstructing the natural connection in residential spaces.