School-age returnees, for example, say they are often taunted by their schoolmates with the term ''gaijin,'' a mildly derogatory word for foreigner. Many young people also say they feel saddened and empty by the emotional reserve that is the norm here: eye contact is rare in Japan, hugging and touching are far less common than in Western cultures, and simple gestures like smiling or holding the door for strangers are almost unheard of.

Companies recruiting workers often frown on Japanese with a foreign high-school or college education as insufficiently adjusted to the ways of Japan, which emphasize outright acceptance of directives from above and group harmony.

Even managers sent overseas by their companies are routinely assigned to back-office jobs until their superiors can be sure that their foreign ways have dissipated. ''When I first returned, after eight years in the United States, my boss would tell me flatly that America had spoiled me, and kept me in a position where I would have really limited contact with customers,'' said Toyokazu Matsumoto, 51, a manager with a major Japanese corporation.

''In a meeting in Japan you are not supposed to react to things quickly,'' Mr. Matsumoto said. ''I still find it difficult not to show some reaction.''

Because of experiences like those, many returning adults, including Mr. Matsumoto, are sending their children to international schools in Japan, where they can escape the heavy rote learning of Japanese schools and maintain their individuality.

With its population dwindling more rapidly than that of any other industrialized country, Japan has begun to debate the extent to which it will need to attract people from abroad to work here. The experiences of expatriate Japanese suggest, however, that even before it comes to terms with new immigrants, this country will first have to learn how to better accommodate its own citizens who have lived abroad.

''The kind of assimilation pressure here is very strong,'' said Kazuhiro Ebuchi, a professor of cultural anthropology at the University of the Air in Tokyo. ''Even people who speak good English are teased here because Japanese should speak English in the Japanese way. Japanese people like to say that we appreciate cultural differences, but this is only lip service. In fact, there is not much place for difference here.''