The man who put the international fashion world on its ear by elevating the so-called ''sack of potatoes'' dress to a high art is skipping across the room. He has just had his picture taken promoting his new line of bed linens, and he seems anxious to dance away from his entourage and the British photographer who has been urging him to ''Tilt your head. Lean forward. Hold it,'' for half an hour.
''Issey, Issey. We need you over here to talk to some more people,'' calls out a voice. With a quick snap of his head and an even snappier smile, the designer stops dead in his tracks, and like a child, obediently turns toward those who have called him.
He is Issey Miyake, Japan's premier clothing designer. In the 20 years that he has shown his fashion collections, this puckish, unprepossessing designer has created a virtual sartorial stampede. Around the world he is recognized as the forerunner of a new breed of Japanese designers currently considered ''hot'' among retail buyers and clothing critics. Collectively they are known as the Tokyo group and include such designers as Yohji Yamamoto and Rei Kawakubo of Comme des Garcons. Indeed the Tokyo-based Miyake Design Studio is thought to have fostered the first indigenous change in Japanese fashion since the kimono.
But more important, Miyake is now considered one of the greatest innovators in fashion history. Observers credit him with mapping out an entirely new fashion direction - one that no longer copies Western design conceits. His designs - inventive, imaginative, derivative of nature in their colors and textures - can appear downright strange to Western sensibilities as they nearly obliterate the body's natural lines. Yet they are undeniably the first significant challenge to traditional French concepts, which have dominated world fashion for more than a century.
Already, sales of his clothing - marketed under three labels: Issey Miyake, I. S. (formerly Issey Sport), and Plantation - are in the $60 million range, a 20 percent increase from one year ago. While many women and men still consider Miyake's vision an unwearable enigma, most New York retailers have already increased their Japanese orders.
''Miyake's vision is unique,'' wrote Brenda Pollen, fashion editor of The Guardian (London). ''His influence upon a whole generation of designers has been formidable.''
''He is one of the greatest designers in the world today,'' says Alan Bilzarian, owner of an exclusive Boston boutique that carries Miyake's couture line.
''His importance will persist, like Yves Saint Laurent,'' says Amy Yates, division merchandising manager for Filene's department store. ''Miyake will remain successful beyond current trends.''
In the West, the Miyake phenomenon has been etched by the unique shapes and fabrics of his clothes that confound traditional expectations of elegance. His 1984 spring collection, considered the best of his career, includes such unusual textiles as ''whisker linen,'' ''cotton embossed by plucking thread,'' ''six-layered woven cotton,'' and ''Japanese paper (raincoat) coated with panlownia oil.''
However, in Japan, a society that emphasizes conformity and the ethic of the group over that of the individual, Miyake's success is seen as the triumph of a personal vision. He is perceived as part of that energetic generation - including the well-known Japanese artist Eiko Ishioka - whose formative years were marked by postwar hardships and who today are comfortable with commercialism and material success. To understand Miyake's significance is to not only plunge to the core of the most revolutionary fashion trend in decades, but to comprehend a bit more fully, the Japanese themselves.
One's first impression of the boyish-looking designer, who is dressed simply in his own collarless shirt and soft black trousers, is that he is charming and delightfully unaffected. He laughs frequently, pays polite and rapt attention to those to whom he is talking, and happily converses in English or through his interpreter in Japanese. But underneath the winning personality one senses a strongly ideological individual.
''Japan is a very conformist society,'' says the designer, who was born in Hiroshima in the late 1930s. ''That is the challenge of creativity there. My generation went through its formative ages during the postwar chaos when American and European cultural influences were very great. It hurt me so much not to be proud to be Japanese. And I had to think, 'What can I do to be truly Japanese but to do so in an international way. Had I been born 10 or 15 years later, I would not have had as many challenges, but undoubtedly my work would be different.' ''
With an early interest in art and design, Miyake attended Japan's Tama Art University, where he presented his first collection, entitled ''The Poem of Material and Stone.'' Later he studied at La Chambre Syndicale de la Couture Parisienne in Paris and became an assistant designer to couture doyens Guy Laroche and Hubert de Givenchy. He also worked in New York under American designer Geoffrey Beene. His first official showing in Paris was in 1973. Since then he has opened every collection there. ''I hope I am the first and the last Japanese designer to have to make my reputation in Paris,'' he says.
While Miyake credits those early apprentice years with teaching him fine French dressmaking techniques, he insists it was the student riots, or so-called ''jeans revolution,'' of the late 1960s that provided the real impetus for his own more democratic definition of fashion.
''I feel very lucky to have lived when the class system began to crumble, when jeans became the garment for all people,'' he says. ''I am not negative about European couture, but I find clothes of that tradition to be a package that people step into. They are fine and beautiful clothes, but they feel stiff and everyone looks the same in them. I want to be different, to be flexible to show the personality of the person wearing the garment.'' Indeed, observers credit Miyake with unparalleled feeling for texture, mass, and volume, for elevating the ''wrap and tie'' style of dressing beyond mere ethnicity to a so-phisticated international style that allows the wearer great flexibility. Miyake actually uses the word ''skin'' when talking about his clothes. ''When I design, it is a little bit like molding clay,'' he says. ''I cut [the fabric], wash it, sew it, put it on me, feel it - the design comes out of the fabric.'' And always what is uppermost in his mind is the relation of the fabric and the body of the wearer - a spatial arrangement that more approximates art than mere design.
''I want the body of the wearer, her individuality, to make the shape of the clothes.''
It is a principle that many observers compare to the original design premise of the kimono. Still others insist that Miyake is providing Japanese women a new outlet for their individuality. ''In my country, people think of fashion as only for the young,'' he says. ''But I am trying to make fashion a challenge.''
Listening to this designer talk about his work and his principles is to be acquainted with an intensity usually associated with an artist, not a fashion designer. Not only has Miyake designed couture and ready-to-wear clothes, company uniforms, and ballet costumes, but he creates and weaves his fabrics. He is now beginning to spin his own yarn. Additionally, he has published two books on his work and has created a traveling exhibition of clothes and unique silicon mannequins called ''Bodyworks.'' His fashion shows - including ''Fly with Issey Miyake,'' and ''Issey Miyake and Twelve Black Girls'' - are considered unequaled in their theatricality. For Miyake this coincidence of art and craftsmenship is no accident.
''Unlike the United States, it is very important in Japan not to distinguish between the artist and the craftsman,'' he explains. ''For us they are one and the same. Our first need is to make something practical, and then to make it beautiful and more fun. That is what Japanese art is. If there one biggest tradition you feel from me, that is it.''