The Mass Museum is the first phase of the Harajuku Expanding Landscape Project, an ongoing 4-phase initiative by Nobuo Araki of The Archetype across 4 sites in the neighborhood. The project is located along Cat Street, in the residential back streets behind Omotesando, an area defined as much by the gaps between buildings as by the buildings themselves. That condition became the organizing logic for the design.

Within a single structure, Araki created 3 distinct exhibition spaces, each with its own entrance and a unique approach sequence. The 3 spaces can function separately, allowing the gallery to adapt the configuration to exhibitions of different scales. The wayfinding between and through the building is designed to register the same kind of blank or residual space found in the surrounding streets: threshold zones, pauses, and lateral moments that accumulate into a spatial experience rather than a direct path.

Several blank spaces are distributed across the site, placed to consciously assimilate with the neighboring buildings and the gaps between them. The intention is that the museum extends the fabric of the street rather than interrupting it, reading as part of the landscape it sits within rather than as an object placed against it. The Mass Museum treats the city not as backdrop but as material, with the structure's exterior and interior logic informing each other through that relationship.