In the first seven months of this year, imported small cars, with engine displacements of under 2,000cc, have increased sales substantially at a time when the overall Japanese car market has been lacklustre.
Although not as strong as the 14 per cent rise in sales of imported cars overall, sales of small cars rose 7 per cent in the period.
Opel's Vita, for example, marked sales of 9,309 units between January and July, compared with 8,230 units between March and December last year, according to Yanase, the sole importer of Opel vehicles.
The Vita is expected to exceed its sales target of 11,000 units to the end of September Although it started with a small base, Renault, which has not been a commonly seen marque in Japan, more than trebled its sales in that period from 536 units last year to 1,745 units.
The rise is largely attributable to the popularity of its small car, the Twingo.
The arrival of the Polo is expected to intensify competition further in the largest car segment in the Japanese market.
In an aggressive push into a fiercely contested segment of the Japanese car market, Volkswagen aims to sell 6,400 Polos in just four months to the end of the year.
The addition of the Polo to the Volkswagen line-up in Japan is expected to help maintain the group's leading position among imported car makers with targeted sales of 46,000 units this year.
The success of Europe's small cars in what is widely considered one of the most difficult markets in the world owes much to the substantial appreciation of the yen over the past several years, which has brought European cars within reach of that market in Japan.
Yanase notes that the main reason behind the Vita's success is its affordable price of Y1.54 million ($14,250), only slightly more expensive than leading models in the segment.
European vehicle makers have also tailored pricing strategy to the Japanese market by offering low-interest loans, making the cars affordable without harming their high quality image.
At the same time, as the emphasis on European-ness at the Polo's launch demonstrated, the image of high quality and sophisticated design associated with European products, particularly German products, has been instrumental in expanding demand for European cars in Japan.
Opel, which, in Japan, is recognised as German, has supported that image with a range of safety features for the Vita, which are unavailable in Japanese cars in the same segment.
The Vita's standard passenger-seat airbags and seat belt pretensioners are significant factors behind its popularity.
The success of Europe's small cars is likely to continue on the back of a spreading divergence of taste among Japanese drivers.
However, there are some clouds in the horizon.
The recent weakness of the yen, which has fallen 26 per cent since its high point last year when it reached about Y80 to the dollar, makes importing into Japan at current prices less profitable.
If the yen weakens further, foreign car makers will have to consider whether it is worth expanding their dealership networks in order to increase sales, points out Enda Clarke, industry analyst at Dresdner Kleinwort Benson in Tokyo.
Meanwhile, Japanese carmakers are not sitting still. Toyota, in particular, which is the price leader, is determined to claw back a larger share of the domestic market where it has slipped in the first half of this year.
The company has said over and over again it will use its pricing power to regain ground, notes Clarke.
With the Polo's launch, Europe's small car makers are expected to take a greater share of the Japanese market.
But whether or not they are able to continue making significant inroads in Japan owes as much to the exchange rate as to their ability to withstand the expected counter-offensive of domestic manufacturers.