According to Famitsu, Nintendo’s (NTDOY) portable 3DS console continued to see huge success during the week ahead of Christmas. It racked up sales of 433,000 units in Japan, up from 333,000 units in the prior week. But weirdly enough, the brand new and heavily promoted Wii U home console wobbled badly as its weekly sales slipped to 122,000 units from 130,000 units in the previous week. This may have been the biggest week in Japanese console market in 2012, so the stakes were high.

To put Wii U performance in context, the old PSP portable console sold 58,000 units in Japan during the same week. It is not an encouraging sign that the more than half-decade old PSP (which was displaced by the PlayStation Vita a year ago) managed to sell nearly half as many units as the brand new Wii U during the holidays. Of course, PS Vita continues to miss sales expectations dramatically — it sold only 19,000 units last week, barely more than a quarter of what its predecessor managed.

Wii U performance may improve dramatically once compelling titles arrive. But during December, it did have “New Super Mario Brothers” and “Nintendo Land” to boost it in Japan. This clearly wasn’t enough. The aging PlayStation 3 sold only 30,000 units and Microsoft’s (MSFT) Xbox 360 barely cleared a thousand units, so the Wii U should have had a clear shot at strong sales performance in the Japanese home console market.

Overall, Japanese game console sales were down sharply from the week ahead of Christmas in 2011. The 3DS is a big hit in 2012 but instead of buoying the entire console market, it seems to be sapping energy from the Wii U and PS Vita.

It’s still early days for the Wii U, but Nintendo has probably started sweating a bit.