One of the things I like about teaching is watching as the students realize there is this whole world outside their small town. Some of the younger ones are very surprisd to learn I don't really speak Japanese. It doesn't make sense to them because everyone else they know speaks Japanese just fine, so why should I have any trouble?
Some get it and talk slowly. Some nod and plow on with whatever crazy topic they were talking about. I'm a very good listener even when it's completely incomprehensible (though I suspect some of it would be even if I did speak the language going on previous experience with elementary school kids.)
Yesterday I had to explain to a little second-grader that I did not write my name with kanji. After excitedly showing me the first character in her name (they had just learned it in class this week,) she asked me how I wrote mine.
"I don't use kanji," I told her. "I write my name with katakana."* (That's the Japanese writing system for foreign words.)
"What? Why?" she asked.
"I'm American. We write our names in English."
Then she got out a pencil and some paper and I showed her both my name in English and the Japanified version.
Then she took off my glasses and I pretended I couldn't see anything. There was some tickling involved to get them back and the teaching moment was gone.
*This makes it sound like I can speak Japanese but a better translation would be. "No kanji. Katakana." and also "I'm American. English names." and then I mimed writing.