The Warner Bros release only lost its pole position last weekend (Jan 13-14) when it was knocked into third place by two openers - local production Penal Colony Of Love, which topped the chart over the weekend, and Sony's Monster House which came in second.
Penal Colony Of Love , an erotic romance starring Shinobu Terashima and Etsushi Toyokawa, came in first despite earning a mediocre $1.33m (Y160m). Released by Toho, it only managed a third of the opening of the distributor's 2006 New Year's release, Suite Dreams.
The second biggest earner during the 17-day key box office period was Yoji Yamada's Love And Honor, which opened in early December, and was the only film to beat Casino Royale on its opening weekend in international territories.
The film has passed the $24.9m (Y3bn) mark, earning it mega-hit status. It was knocked out of first place by Eastwood's film, but continues to be a local favourite.
Rather than Christmas when people are still working, it is New Year (oshogatsu in Japanese) that is a key box office period in Japan.
Love And Honor has been selected as the opening film of the Panorama section at next month's Berlin International Film Festival, while Letters From Iwo Jima will screen out-of-competition.
Overall box office for the New Year's season has been pegged at 85% of last year's take, with more mid-range hits but a lack of tentpole pictures such as last year's Harry Potter And The Goblet Of Fire ($83.7m), Yamato ($42m) and Mr. & Mrs. Smith ($39m). The same has been true of the year overall.