TOKYO -- With only a few precious shopping hours left until Valentine morning, downtown department stores here were jammed to gridlock with young women frantically buying "duty chocolate" for Mr. Wheels, Mr. Meals, Mr. Real and The Boss.

In a characteristic twist on Western traditions, Japanese pop culture has turned Valentine's Day into a sort of Sadie Hawkins Day for working women. Driven more by social requisite than by romance, women buy expensive chocolates -- known here as giri choco, or "duty chocolate" -- for all the men in their professional and personal lives.

Department stores and candy boutiques catering to this week's jostling hordes of immaculately dressed female shoppers set up massive displays of ornately wrapped chocolates. To create the right mood, an Osaka store has featured a life-size, one-ton chocolate copy of Rodin's famous statue of a passionate embrace, "Eternal Spring."

Comic books aimed at young women and popular magazines such as Pucci-7 and Hanako, where the smart set gets its marching orders, have printed lists of the type of men to whom single working women must give chocolates on Thursday morning. These offer a nice picture of the social structure young Japanese women are creating these days as more and more of them enter the work force and delay marriage until age 30 or later.

On the personal side, single women here tend to divide the men in their lives into specific categories, each referred to with the suffix "-Kun," or "Mister."

A man with a fancy car, reliable for transportation to particularly important events, is known as Asshy-Kun, or "Mr. Wheels." A gourmet with deep pockets, willing to take his date to one of the exorbitant French or Italian restaurants in the four-star hotels, is known as Meishi-Kun, or "Mr. Meals."

Then there is Mitsugu-Kun, or "Mr. Sugar Daddy." This is a derisive term for men who use large chunks of their salaries buying jewelry and vacations for their girlfriends. In contrast, there is Keepu-Kun. That name, taken from the English word "keep," refers to a nice guy the woman keeps in the back of her mind against the day when it's time to think about marriage.

Best of all, though, is Honmei-Kun, a name that means "Mr. Real," Japan's equivalent of "Mr. Right." A television drama this week about Valentine's Day depicted the tribulations of a thirty-ish "Office Lady" as she tried to find a chocolate present for her true love that would let him know he is her Mr. Real.

In addition to all these people, the single working woman is also expected to purchase "duty chocolate" for The Boss -- that is, the various men above her in the strict hierarchy of Japanese companies.

To help women fulfill this duty, the Tokyu Department Store here has given customers a handy "Valentine Check List" noting all the men for whom they must purchase chocolate. The roster starts with the president of the company and moves down through the department head, division head, section chief, and their various assistants.

Much of this fervor is aimed at OLs, or "Office Ladies," the women who change from their designer clothes into the company uniform in the corporate locker room each morning, then spend the day typing letters and serving green tea in the office. But the Valentine's Day virus has also infected female professionals, managers and entrepreneurs.

"I have my own business," laughs Tokyo interpreter Itsuko Sakai. "I don't have a section chief. It's ridiculous that I should be out buying duty chocolate. And here I am with this bag from Mitsukoshi {Department Store} full of chocolate I'm giving to men."

For the most part, gifts of Valentine's Day chocolate here tend to be small.

The huge red heart-shaped boxes that Americans have been giving their valentines for years are taboo here. Instead, the normal gift is a $5-to-$25 package containing a few ultra-fancy bonbons or truffles. Foreign brand names -- Godiva, Morozoff, La Tour d'Argent etc. -- are in, as are English-language messages -- e.g., "Selected ingredients blended into flavorous taste" -- on the package.

As is common in a society where the wrapping can be as important as the contents, valentine chocolates are beautifully presented. Typical is a gift labeled "Pierre Dore, Paris" that costs $5.60 for a box smaller than a cigarette pack. You remove the gold ribbon and maroon wrapping paper, open the box, dig through crimson tissue paper and unfold a layer of gold foil, thus revealing an inside box that contains a greeting card and precisely two truffles, each wrapped in cellophane and resting on a paper tray.

Typical working women feel a need to buy a dozen or so chocolate gifts for valentines. A survey this week suggests that they will pay about $6 apiece for the men in the office, $15 or more for the Messrs. Wheels, Meals etc., and something above that for the men they really care for.

All of this is an unmitigated boon to the department stores and chocolate companies, which invented and promoted the idea that women must give chocolate on Valentine's Day. In a chocolate-loving country, Valentine Week produces about 10 percent of the candy industry's annual sales, according to trade figures.

While men are on the receiving end for Valentine's Day, they have their own "duty chocolate" obligation coming up precisely a month from now.

About five years ago, the candy industry decreed that March 14 would be "White Day," when men must return the valentine favors by giving white chocolate gifts to women.

That too has become accepted fashion. And in a nation where fads are everything, no man dares buck the trend.