In the Mitla district of Tokyo, a unique architectural project has quietly defied the city’s rapid cycle of demolition and redevelopment. Arimasuton, a four-story concrete building marked by jagged ledges, asymmetrical windows, and an unfinished aesthetic, recently completed its construction after more than two decades of labor by its architect and builder, Keisuke Oka.

Unlike Tokyo’s typical modern buildings characterized by glass and steel, Arimasuton is made entirely of exposed concrete, showcasing raw textures and embedded patterns. Oka began the project 21 years ago with the intention of creating a structure that would endure for over a century—an explicit challenge to Japan’s standard practice of tearing down buildings after relatively short lifespans. Its distinctive, improvised design features a range of decorative motifs, from geometric forms to depictions of grapevines, achieved by imprinting everyday objects into the concrete during construction. The building also incorporates an intentionally open interior void revealed by arching beams and a precarious-looking staircase reminiscent of M.C. Escher’s work.

The ground floor is designated for retail use, while the upper three levels include living spaces such as a bedroom and a living room with a small kitchen. The building stands in stark contrast to neighboring high-rises that adhere to contemporary architectural norms, emphasizing Oka’s intent to create a lasting, personal statement. Terunobu Fujimori, director of the Edo-Tokyo Museum, praised the building’s expression through concrete and Oka’s hands-on approach, calling it one of the most representative concrete structures in modern Japan.

Oka’s journey to realizing Arimasuton was unconventional. After being advised to take a break from architecture during his studies, he immersed himself in Butoh, an avant-garde Japanese dance form, gaining insights into improvisation and self-expression that influenced his architectural philosophy. Later, he contributed to the building’s construction almost entirely by himself, learning skills typically delegated to specialized trades. This labor-intensive process was complicated by numerous setbacks, including a confrontation with a redevelopment plan that forced Oka to relocate the structure roughly 40 feet—a costly and complex operation.

Despite criticisms from some local commentators labeling the building a nuisance or dangerous, Arimasuton has proven resilient, sustaining no damage during the 2011 magnitude 9 earthquake in northeastern Japan. Oka employed a special low-water-content concrete mixture to enhance durability and longevity. His commitment extended to creative problem-solving on site, such as wrapping plywood formwork to prevent exposure to harmful formalin, which resulted in unique concrete patterns incorporated into the design.

The project took a significant personal toll on Oka, leading to financial difficulties and the end of his marriage, with ongoing support coming from family and sales of building-related merchandise. A diverse group of collaborators, including manga artist Hideki Arai, contributed to the building’s realization. Arai, inspired by Oka’s story, documented the process in a short manga and assisted with some construction.

With the building now certified as safe, Oka is focused on completing the interior, which remains a work in progress. He plans to live in the upper floors and lease the ground-level retail space. Looking ahead, Oka envisions Arimasuton becoming a museum or gallery and hopes the structure will endure for another 150 years, serving as a lasting testament to individual dedication and an alternative approach to architecture in Tokyo.