Mr. Tanaka works out of a small, garage-like studio underneath his home in Tokyo’s Adichiku prefecture. “This is maybe a half or a third of the workshop,” says Cohen. “It’s a total mess, full of dust. When we first got there, we thought, ‘OK, he hasn’t been down here for 30 years.’ But he knows exactly where everything is. We’d say, ‘Oh, we need this piece’ and he’d go straight to it and come back a second later. It’s like one man’s kingdom.”