Olympics in Tokyo. Tange’s arena — with its high mast and violently sloping roof, its form like a discus emerging obliquely from the earth — was a masterpiece of engineering, and remains the most breathtaking example of Japanese Modernism. Speaking to me about the building in October, in the glassed-in penthouse library above his firm’s Tokyo offices, Kuma became animated. I had only met him a few minutes earlier, in the cramped main quarters, when he swiftly emerged from his tiny, cubicle-like space in the far corner. Kuma is tall, informal — he was wearing stonewashed jeans, and a striped T-shirt under a nylon jacket with frayed and shredded shoulders — and he greeted me with a quick handshake, as if I were another employee. But he grew noticeably excited speaking about Tange’s gymnasium. “Tange treated natural light like a magician,” he said, discussing the way the panels on the ceiling reflected light bouncing off the swimming pool. “From that day, I wanted to be an architect.”

And yet Tange’s work — aggressively modern, wresting enormous form out of space, deploying the latest synthetic materials, an imposition on the landscape and an attention-grabbing demonstration of what architecture could do in a city that only 20 years earlier had been comprehensively destroyed by American bombs — could not be further from Kuma’s own aesthetic. He is the most famous Japanese architect Americans have never heard of, ...