What language does the movie "Lost in Translation" focus on?

While Japanese is the main language featured, English plays a vital role in "Lost in Translation" as it becomes the common thread that binds Bob and Charlotte together. As native English speakers, the two main characters are able to overcome their shared loneliness by conversing in their mother tongue. As such, English serves as a way for them to establish a connection and create a sense of familiarity in an otherwise foreign world.