There are many skills a foreigner needs if he wants to live in Japan, like how to say biiru o kudasai (beer, please) and hen na gaijin desu (I'm a strange foreigner), two of the first phrases you learn here for some reason. Learning to to kneel on tatami mats for hours on end with your legs not falling asleep is helpful, too. Another skill that comes in handy is the ability to speak extra-difficult English, which allows you to communicate with other native speakers without Japanese understanding. If you wanted to make a comment on how cute a certain girl is but keep her from letting on, you might say "I am quite infatuated with the member of the fairer gender standing adjacent to you." The trouble is, you never know for sure how good their English might be. Once in a KFC, I made a comment to a friend about how the word "Colonel" -- kaanaru as the Japanese say it -- sounded like the English word "carnal." Imagine my surprise when the Japanese girl at the register said "Yes, I've often thought that" to me in perfect English (she'd grown up in Los Angeles). Another good way to speak in code around Japanese people is to use Pig Latin, which will scramble any sentence to incomprehensibility in short order. When I taught it to my son, he thought it was the coolest thing in the world, and soon had all his friends speaking it.
You never know when someone will speak really good English in Japan.