It was only seconds before the climax of his first New York show last April. Backstage, at the cavernous West 14th Street Armory, a fuse blew and the lights went out. With eerie flashes from the strobes lighting up the runway, a slight figure darted forward into the thundering applause. Yohji Yamamoto, the 39-year-old Japanese designer, fresh from recent triumphs in Paris, had just brought Seventh Avenue cheering to its feet. The applause underscored not only Yamamoto's success but also the explosive changes that are rocking the fashion world, turning Tokyo into the Milan of the East. Better known Japanese designers like Issey Miyake, Kenzo and Hanae Mori have been established in the West for much of the last decade. But now comes a new wave of Far Eastern avant-gardists—Yamamoto, Rei Kawakubo and Mitsuhiro Matsuda. "Yesterday it was the Italians. Today, the Japanese," observed Hubert de Givenchy. "Who knows, tomorrow it might be the Chinese." Chimes in Jon Weiser of New York's trend-setting Charivari stores: "Of the new breed, Yohji is certainly the leader."

In Japan, fashion's newest star is frequently stopped on the street and asked for his autograph. But such rock-star adulation has not softened Yohji's stringent, Zen-like sense of design. Among his followers he has gained a reputation for radically conceived men's and women's clothes, cut away from the body. "I think to fit clothes tight on a woman's body is for the amusement of man," he announces. "It doesn't look noble. Also it is not polite to other people to show off too much." The Yamamoto view of fashion is diametrically opposed to the swishy grand luxe of French haute couture. "My clothes are very different from others," he says. "Every time I do a show people say, 'Yohji, why do you use such dark colors? Why do you make dresses in such a sad mood?' "

To achieve the exquisitely simulated "poor look" his fans adore—and that sells for up to $1,200—Yohji hand-treats his fabrics at a factory in Gifu, a well-known textile center two and a half hours from Tokyo. There, using the friction of tiny pebbles, he stone-washes leather in huge steel tanks. Bolts of wool and cotton are dunked by workers in the Nagara River and sometimes dried along the banks. For Yohji, this process of breaking in fabrics is instinctive. "When I was a boy and my mother bought me a new shirt," he recalls, "the first thing I wanted to do was wash it before wearing it."

Yamamoto grew up a lonely child in the Shinjuku district of Tokyo, a neighborhood dotted with cheap bars and cabarets. When he was 2, his father, Fumio, who had been in the restaurant business, died of undetermined causes on a transport ship en route to the Philippines. "My mother, Fumi, was a typical Japanese war widow," says Yohji, pausing to sip his green tea. "She made up her mind never to marry again, to live alone and work very hard just for her child."

Yohji was 12 when Fumi, a dressmaker, transferred him from public school to the Ecole de L'Etoile du Matin (School of the Morning Star), an exclusive French Catholic school near the Imperial Palace. His future business partner, Goi Hayashi, was a classmate. Both men remember their first encounter in the schoolyard. Goi threw a rock at Yohji. "It was a place for rich people's children," says Yamamoto. "I felt I was different from the other boys." About his childhood, Yohji says, "Even then the most important part of me was woman. I was born from woman and I lived for about 20 years with only woman. When I was at kindergarten, my most intimate friends were always girls. I always fought with boys. Girls were for me mikata—a friend, an ally."

In 1966, Yamamoto graduated from Keio University with a law degree. "My friends were secure about their future because of their connections," he says, "but I had no connections. So I thought it over and over and I decided to change my future. I decided not to become a businessman."

With Fumi's reluctant blessing he entered Bunka Fukuso, the famous fashion school where Kenzo had also studied. "I just wanted to help my mother," he explains. "I didn't know there was a kind of business called designer." With prize money he won at graduation, Yamamoto went to Paris in 1968. It was a harsh time for Yohji, who rented a dark narrow room in a cheap Left Bank pension, making the rounds of fashion magazines and department stores—never with any luck.

Back in Tokyo the following year, he free-lanced and helped Fumi in her boutique—designing for nightclub entertainers and housewives. But in 1972 he announced to his mother that he wanted to start his own ready-to-wear company. "Yes, you do it," Fumi said. "It is up to you." With her help (Fumi has been working for the firm ever since), he struck out on his own.

Like his sojourn in Paris, those first years were intense, often bleak. But slowly Yamamoto's luck changed, and in 1977 the press and public went wild over his breakthrough collection at the Bell Commons in Tokyo. Meeting with his staff after the show, the normally restrained Yohji burst into tears. "From then on," he says with a twinkle, "it is a very common success story. So it is not as interesting."

Yohji's modesty hides an intense professional drive. "I am hungry in my heart," he has said by way of explaining his ambition. With his clothes now selling in 10 countries around the world, Yamamoto expects to gross $15 million by the end of the year. "I think he has a big future in the U.S.," says Bloomingdale's vice-president for fashion direction, Kal Ruttenstein. "It will take a bit of time. His clothes are not easily understandable to the masses. But in sophisticated cities and stores, customers will catch on that something different is going on."

Right now Yohji shares his modest one-bedroom apartment, a 10-minute bike ride from the office, with two cats and one dog. Divorced, Yamamoto has a 13-year-old son who lives with his ex-wife.

In the midst of planning his Paris show for later this month, Yohji has his eye on the future. "After finishing all my fight, all my struggle," he says, "I want to stroll along the street with my dog. I will love to be old man."