Hey Pratyush, yes it is possible to open a webpage in a specific language like Japanese, not only webpage you can set any language for a browser by using setPreferences() method. You can set any languages supported by browser in the following way:
FirefoxProfile profile = new FirefoxProfile();
profile.set Preference("intl.accept_languages","jp");
Web driver driver = new FirefoxDriver(profile);
driver.get(google.com);
The above code snippet will open google in Japanese Language.