“Letters From Iwo Jima,” which opened at five U.S. theaters Wednesday, has already dazzled the Japanese.

Clint Eastwood’s Japanese-language companion piece to “Flags of Our Fathers” has dominated at the Japanese box office during the past two weekends. Drawing $13.3 million in its first 11 days days through Tuesday, pic’s nearly matched the $13.4 million “Flags” has taken during its two-month run in the country.

And with a decline of only 26% in its second weekend, “Letters From Iwo Jima” will almost certainly have long legs in coming weeks. “Letters” grossed $3.2 million at 401 playdates last weekend to top the launch of “Eragon” by 46%.

Pic, titled “Iwo Jima Karano Tegami” for the Japanese market, tells the story of the WWII battle from the Japanese perspective. It received strong reviews locally along with a Nov. 15 world premiere at Tokyo’s Budokan arena attended by Eastwood and the Japanese stars.

The presence of pop star-turned actor Kazunari Ninomiya in the cast is helping “Letters” attract a younger demo.

“This is such a unique movie that it’s become a cultural phenomenon in Japan,” noted Warner Intl. prexy of marketing Sue Kroll. “We think we’ll have an excellent run.”

Warner execs predicted earlier that “Letters” could top $40 million in Japan. WWII pics have racked up respectable rather than blockbuster perfs in Japan in the past. “Pearl Harbor” topped $56 million, “Saving Private Ryan” took $37.2 million and Terrence Malick’s “Thin Red Line” $10.6 million.

Kroll explained that Warner will wait until February to roll out “Letters” in other international territories, partly to lay the groundwork for long-lead critics’ screenings and partly because it needs to finish opening “Flags” in foreign territories. It’s targeting the weekend before Oscars for “Letters” openings in the U.K., France, Germany and Australia.

And rather than dubbing the film, Warner will unspool “Letters” in the Japanese language with subtitles in all markets.

Eastwood developed the idea for “Letters” while shooting “Flags,” which has shown moderate traction at the box office so far with $33.6 million domestically and $21.4 million overseas — most of that in Japan, with France and Italy generating only mild biz.

“Flags” opens in the U.K. this weekend, followed by Germany next weekend and Spain in the first frame of 2007.