In the shadow of the sleek glass-and-steel towers that dot the modern skyline of Tokyo’s Mita district, a monument to idiosyncrasy has passed a major hurdle on its two-decade road to completion.
The “Arimasutonbi-ru” (Arimasuton Building) looks like an attempt to overturn every modern architecture convention.
It rejects smoothness, symmetry and polish. Irregular openings, protruding forms, handmade textures and expanses of exposed, board-formed concrete give the structure the raw, stubborn presence of something carved out of resistance rather than designed on paper.
The Arimasutonbi-ru earned the nickname “the Sagrada Familia of Mita” after Spain’s famously unfinished cathedral, for the two decades it took for completion.
Its name is a playful composite of creatures from land, water and sky: “ari” means ant, “masu” means trout and “tonbi” means black kite.
The final syllable also carries a nod to Le Corbusier, the modernist master whose name is rendered in Japanese as “Ru Korubyujie.” The last element, “biru,” means building.
The craftsman behind the Arimasutonbi-ru is Keisuke Oka, 60, a first-class registered architect.
He did not build the 12-meter-tall structure with a fleet of heavy machinery or a large construction crew.
Instead, he built it with his own hands, a pickaxe and a radical philosophy of “self-building,” which challenges the ephemeral nature of Japanese urban architecture.
The reinforced-concrete building stands about 12 meters tall, with four stories above ground and one basement level. Oka plans to use the basement as an art gallery, the first floor as a rental shop and the upper floors for his private residence.
On March 10, the building passed its final legal inspection, marking a major milestone.
The project began with a casual remark from his wife shortly after they married: “You can design houses, right? You can do carpentry too, right? Then why don’t you build the house we’re going to live in?”
At the time, Oka had just obtained his architect’s license at age 30 and was struggling with a sense of inferiority as he watched his peers move ahead in their careers.
In September 2000, after searching across Tokyo, he bought a 40-square-meter plot of land for 15.5 million yen ($97,500). Yet, when it came to the actual question of how to build the house, he found himself groping for a way forward.
The breakthrough came during a workshop led by Osamu Ishiyama, an architect Oka admired.
There, he was struck by the idea of “self-building” — taking on everything from design to construction himself. Ishiyama encouraged him, saying, “Go with that.”
Construction began in November 2005. Oka initially expected the work to take about three years. Instead, it took a year and a half just to excavate the basement, using only shovels and pickaxes.
From assembling rebar to pouring concrete into molds, more than 100 people — including friends and others he met through social media — lent a hand along the way.
‘IMPROVISATIONAL’ DESIGN
There are no detailed blueprints. The design evolved through “improvisation,” with ideas emerging in the course of construction.
Oka found inspiration in “butoh,” a form of Japanese dance-theater in which he was deeply involved during his 20s. He applied to the building process a butoh-like principle: move the body before the mind has time to impose a fixed plan.
In contrast to the short lifespan of many buildings in Japan, Oka was exceptionally particular about his building materials. For the concrete, he reduced the water content as much as possible, mixing it into a highly viscous paste and layering it little by little.
Although low-water concrete is far more physically demanding to handle, it produces extraordinary strength. Experts have certified that the building could stand for 200 years.
It reportedly did not suffer a single crack during the 2011 Great East Japan Earthquake, which devastated a wide swath of the Pacific coast in northeastern Japan and also shook Tokyo.
Oka’s commitment to self-building is rooted in his experience as a laborer. After studying design at a college of technology in his hometown of Fukuoka and briefly working for a housing manufacturer, he spent a decade as a scaffolder, rebar worker and formwork carpenter.
During that time, he sensed a profound disconnect.
“Even though many craftsmen are involved on-site, there is almost no contact with the architect,” he said. “It feels as if the finished building is entirely the product of what the architect imagined in his mind.”
The reason, he felt, was that the completed building simply reproduced the image set down in the blueprint.
“The distance between the craftsman and the architect is too great,” Oka said. “I felt it shouldn’t be that way.”
STANDING FIRM AGAINST REDEVELOPMENT
The road to completion was not without its twists and turns.
In January 2009, an employee from a major real estate company arrived unannounced to tell Oka that his plot was part of a large-scale redevelopment plan.
Asked to vacate the site, Oka held firm, determined “not to give up a single inch” so he could create something of genuine quality.
He began actively sharing information about his project on social media to raise its profile. Gradually, his circle of supporters grew to include not only architecture and art students but also prominent industry veterans.
Ultimately, the building was spared demolition on the condition that it be moved — literally shifted 10 meters back from the road through a process known as “hikiya.”
The method involves relocating an entire building by detaching it from its foundation and moving it to a new position using jacks and rails.
Looking back on the unexpected change in plans brought about by the redevelopment, Oka speaks with pride.
“Despite some unexpected developments, something even better than I imagined was created,” he said.
Although the structure itself is complete, some interior work and painting remain, with final completion still a few years away. The kitchen and bathroom have yet to be installed, meaning that it will be some time before he can move in.
Once everything is finished, Oka intends to sell the building and continue living in it as a tenant.
“I may have 30 or 40 years left in my life,” he said. “But even after I’m gone, this building can be used for another 150 years. A building with such a long lifespan is a total bargain. I hope it can be used as a gallery or a museum.”