Every Sunday morning, the 17-year-old girl who calls herself "asuka" for such occasions leaves her home in Kamakura and takes the train to Harajuku, a trendy Tokyo section whose shops and restaurants cater to the young.

Behind a clump of bushes in a park she strips off her schoolgirl garb and changes into her street-dancing uniform -- a bizarre outfit consisting of a black gown bedecked with beads and medallions over what look like bright green pajamas.

Then she joins about 50 similarlyl dressed friends, boys and girls, in a circle around a portable cassette player and dances into the afternoon. They sway for hours to the pop songs and rock music, occasionally chanting something unintelligible, watching each other and being watched by passersby.

The street, by midafternoon, is packed with thousands like her. It is more than a mile of dancing, lively color -- purples, blues, shocking pinks, bright reds -- and blaring cassette tapes.In staid, well-dressed Tokyo, there is nothing else like it. They are the "take-no-ko" and for nearly two years they have alternately shocked and puzzled adult Tokyoites.

Is it a rebellion against Japanese conformity? Or just a bunch of kids showing off and having fun? Probably somewhere in between. "Asuka," who won't disclose her real name, likes the attention.

"We want everyone to see us," she said, between acts one chilly Sunday. While she dances, she explained, she is "medatsu," a word roughly meaning "conspicuous." "This is another me," she said.

If it is a youth rebellion, it is a timed one, carefully trimmed and manicured to fit the Japanese style. No whiffs of marijuana drift over the crowd. Obliging police block off traffic to afford them a wide boulevard for dancing. There is rarely even a scuffle and the only hints of unwholesomeness have been stories about middle-aged voyeurs peeking into the bushes used by girls as dressing rooms.

The "take-no-ko" street scene began as an off-shoot of the disco movement, which swamped Tokyo in the mid-'70s like many other Western fads. Young teeny-boopers at first flocked into the discos in specially-bought vivid costumes but the police soon stepped in to discourage their hanging around drinking spots. So they took to the streets.

A large contingent now is made up of Elvis Presley devotees, boys with duck cuts and leather jackets who perform elaborate and energetic dances to the beat of 1950s rock 'n' roll.

They tend to be more serious about their work and some regard it as their mission in life to recreate the Presley period. "I want to restore the 1950s," declared Tetsuya Nakamura, an 18-year-old student who dresses in an American college athletic jacket and saddle oxfords. "That is my dream."

Nakamura is leader of the "Blue Velvets." ("It was just such a beautiful name," he explained). The boys wear typical 1950s street clothes and the girls wear saddle shoes, bobby sox, leather jackets and hair-bows. They tend to look down on the disco-garbed set, which prefers current rock and pop songs.

Their devotion to the American 1950s is puzzling. A "Blue Velvet" member, Kunio Nakagawa, recalls the great power of the United States in that period, when it was helping Japan economically, and looks back on it nostalgically as "a pure and genuine time." Asked if he meant the era before Watergate and Vietnam, he said, "Yes."

If being seen is the chief goal, it is not altogether a whimsical motive. The Japanese news media has all but devoured the "take-no-ko" scene, picking it clean in countless articles and television shows. Being filmed for television is a great thrill and many of the performers hope to be discovered as recording artists and television stars of the future. Nakamura readily admits he hopes to get his start as a recording star in the streets of Harajuku.

"Take-no-ko" can literally be translated as "the bamboo children," but those looking for some essoteric significance will be disappointed. The name is taken from that of Takenori Otake, the 30-year-old clothes designer whose styles captured the hearts of young disco dancers several years ago. His family name translates as "great bamboo" and it was affixed to the young dancers collectively by the mass media because the designers' insignia was on their clothes.

Otake began designing seven years ago in his home and has profited considerably from the media sensation achieved by his customers.

He now operates three shops for "take-no-ko" clothing in Harajuku and has corner outlets in seven department stores around Japan.

Otake has been burned by the media, which accuses him of manipulating the "take-no-ko" movement for his profit. His sales manager, Hiroshi Ikeba, has defended the establishment, contending that it merely makes clothes, not movements. The costumes are cheap -- ranging from about $15 to $35 -- and can be afforded with parents' allowances.

Through countless interviews, Ikeba has become a pop-sociology commentator on the "take-no-ko" scene and sees in it no signs of serious youthful rebellion against conformity. They are usually boys and girls from middle-class families -- students or dropouts of the working young -- who like to have fun on weekends, he said.

"There is nothing for kids 16 or 17 to do," said Ikeba recently. "There is no suitable playground. They have sports and movies but those cost money. They wanted a place to do what they want to do and Harajuku suited that. They are not seriously thinking of rebelling against society."

The movement is distinctively Japanese in that it relies heavily on a group identification. Besides the "Blue Velvets," there are the "Phantom Play Group," the "Rockabilly" group, the "Lollypops Rock and Roll Club" and dozens of others.

Just forming a club for partying is part of the motivation. The "Blue Velvet" leader, Nakamura, explained that college students or company employes have natural built-in groups to join and party with.

"The young people have no party tradition like those in companies and colleges do. We have no chance, those in our generation. So we decided to make our own parties in the 1950s way."