House in Ohasu is a 645-square-foot residence in Higashi-Osaka, designed by Yousaku and Madoca Tsutsumi of arbol for a family of 3 on a compact urban site surrounded by temples and Japanese-style row houses. The clients requested Peranakan architectural features: the hybrid building style of Southeast Asia characterized by arched arcades, colorful facades, and a particular relationship between interior and exterior space. Rather than replicating Peranakan elements directly, arbol synthesized them with the logic of the Japanese row house tradition of the neighborhood.

The formal solution is a sequence of arches that vary in size and height as you move from the entrance toward the back of the house. The rooms progress in order: front yard, living-dining kitchen, courtyard, utility room, and bedroom. Each threshold between zones is defined by an arch, and the height of the ceiling and the scale of the arch increase as you move deeper into the plan. The arches overlap in depth when viewed from the entrance, creating layers of shadow that give the narrow house more visual depth than its footprint would suggest. Some arches are partially cut away, which produces a sense of openness similar to the pilotis passages of Peranakan arcade architecture, where covered exterior space transitions to interior without a clear boundary.

The house is lifted slightly above grade on a cantilevered facade, with a front yard and an internal courtyard sitting under the same roof as the rest of the building. This keeps the outdoor zones private and connects them directly to the living spaces without the separation of a conventional exterior wall. Natural light enters vertically through the courtyards and changes in quality through the seasons and the day, which shifts the character of the interior alongside it. The walls and ceilings are finished in natural plaster, and wooden sprayed insulation is used throughout. Multi-layered glass with some vacuum glass panels improves thermal performance, and a second-type ventilation system filters external air before circulating it through the house. The site was previously occupied by an adjacent aged row house, which was partly cut and rebuilt as part of the project.