What is the film called with Bruce Willis in as being trapped a slave by Japanese?
You're likely thinking of the film
"Hostage" (2005), starring Bruce Willis. While the film doesn't feature a Japanese storyline, it involves Willis' character, a former hostage negotiator, being taken hostage himself by a group of criminals who are holding a family captive.
It's possible there's some confusion with the details, as it's not a common plot point for Willis. To help identify the correct film, can you remember any other details about the plot?