the cheap chic teen retailer with sprawling ambitions

The Takashimaya store on Manhattan's Fifth Avenue was spare, exquisite, and often too quiet for its own good. It closed in June. Five months later, only the Japanese department store's marble floors and high ceilings remain. The six-floor, 30,000-square-foot space has been transformed into a glittery, dizzying showplace for Forever 21, the cheap chic teen retailer with sprawling ambitions, not the least of which is wanting the grown-up world to take it seriously.

On a late November morning the day before the store is to open for the first time, Linda Chang takes a moment to contemplate her family's ambitions. "It's pretty historic that we're on Fifth Avenue," she says. "We've tried hard not to make it feel like fast fashion." Chang has recently become the slightly more public face of the very private family that owns Forever 21, and she's still feeling her way into the role. Chang is 29 with an undergraduate business degree from the University of Pennsylvania, and she's been leading the marketing department for the past two years. One day she'll likely run the nearly $3 billion, 477-store, 35,000-employee chain. For now, Do Won and Jin Sook, or Mr. and Mrs. Chang, as everyone at Forever 21 calls them, are still very much in charge. Mrs. takes care of the merchandise; Mr. takes care of everything else.

He is here today, a youthful-looking man in his 50s wearing a dark blazer, jeans, and a wool scarf. No one dares approach him uninvited. Linda is far more outgoing. "This is our rock-and-roll section: sequins, black lace, leopard, some leather, a mix of the wild things, our faux fur, crochet," she says, sweeping her arm across just some of what's on the first floor. She's dressed modestly in a Forever 21 black T-shirt and jeans with a boyfriend blazer. Her necklace, of interlocking Cs, is Chanel.

A 20-foot chandelier dangles from the mezzanine above, and flecks of gold paint shimmer on the walls. On other floors, Linda points out plaid shirts, Nordic ski sweaters, sweaters with elbow pads, military-style jackets, capes, draped work dresses. On and on it goes: Forever 21's buyers—and shoppers—expect the stores to offer every trend. "Mrs. Chang oversees all the merchandise," says Linda of her mother. "But she doesn't travel to store openings. She says: 'I'll get you the product. You sell it.' "

I notice a pair of faux-leather lace-up ankle boots that look a lot like the Jeffrey Campbell ones I'm wearing: The style is the same, so are the combination of hooks and holes for the laces and the distinctively shaped heel. Forever 21 sells the boots for $35.80, less than one-quarter the price I paid. I mention them, and Linda says brightly: "You should buy another pair here." Fashion watchers will find a lot more that looks familiar in Forever 21.

On the sixth floor, we stop in front of a revolving rack suspended from the ceiling. "That's one of my sister's favorite things," Linda says. "The clothes rotate around, and you can stop it when you want. It's from the movie Clueless. My sister wishes she could have one in her room." Linda's sister is Esther, who graduated from Cornell University with a degree in fashion and merchandising and at 24 is the head of the company's visual display team. She's been up all night putting the finishing touches on the store. "Esther had one week to set it up. We're fast. Everything we do is fast. W