Many students over the years asked if it is good to use watching movies as a way to study. Essentially I would say that it is a good thing. I have always believed that we need to enjoy studying English which acts as a self motivator. So interacting in English in a way that we enjoy is a great enabler for your language skills.
That's the key though. There has to be something active to the process. You could, for instance watch the movie once purely for entertainment and at that time you can pick up some listening practice and basic comprehension if you aren't focused on the Japanese subtitles. But they you should watch the movie again. Either with English subtitles or none at all. Have a notepad nearby and take notes of words, difficult to hear points or idioms that you encounter as you go. Pause the movie. This time you are studying. After you finish, watch it again, purely in English with no subtitles at all and just practice listening and use the points you took notes about as review opportunities.
The key to any study success is to do it actively and to review what you have learned, or even better use the new expressions. Studying passively can get some results but it will take far longer for them to be noticeable than if you actually approach it as a learning opportunity.
That being said, just watching the movies with English voices and hopefully subtitles is better than not doing it all. This is just my suggestion for how to get the best results.