A multi-story complex building planned in the heart of Tokyo's residential area, comprising five above-ground floors that include owner residences and rental offices. The design incorporates protruding and recessed rectangular concrete volumes that overlap, with displaced sections redefined as external staircases, terraces, balconies, and eaves. Various external spaces are intricately woven into different parts of the building, creating spaces like intricate pleats.

Despite strict setback restrictions and shadow regulations in the urban residential area, the building maximizes volumetric space by utilizing factors such as "sky ratio". The upper floors are setback, and the overall volume is segmented to harmonize with the surrounding cityscape.

External staircases are arranged in such a way that it twines around the building volume. Although they appear to create complex paths, they serve as straightforward evacuation routes. The second-floor offices have direct access from ground through these stairs, clearly designated for third-party use. In contrast, residents on upper floors use the north-side elevator, preventing the line of flows between office users and residents from intersecting.

In order to organise the overall structure, in which the volumes are complexly offset in the XY axis direction, a consistent study flow using 3D CAD was established to improve the efficiency of design. Original calculation tools were developed using Rhino+Grasshopper scripts for sky ratio and shadow analysis, allowing real-time verification of legal compliance while conducting complex volumetric studies of the complex form.

As the plans for each floor were different, we modelled everything in the 3D data, including the facility piping, and conducted facility layout studies and visualisations while comprehensively verifying design, function, constructability and maintainability, and used this information in discussions with the constructors.

Although compact, the building, located in Tokyo's residential area, incorporates diverse intermediate spaces connecting the inside and outside. This design allows residents/office users to feel the gradation between the city's landscape, activities and natural elements such as wind and greenery, creating an experience that truly embodies the essence of urban living/working.