Korean as a common language

At my Korean language hagwon, there's only two people in my class; me and a college student from Japan. In class we only speak Korean, because... well.. it's Korean class. But, as I realized quickly, if I wanted to talk to him outside of class, I was going to have to speak Korean too, since his English comprehension skills were extremely low. As it turns out, this friendship has turned into a great way of learning Korean for the both of us. I'm accustomed to only speaking Korean until my grammar or vocabulary skills run out on me, or my head starts to hurt, then I switch back to English. But with my Japanese friend, I can't do that. Talking with him often, I think, has really helped my Korean fluency. We're both at the same level, grammar and vocabulary wise, so we rarely use words that the other doesn't understand. I'm sure every Korean around us must be trying so hard not to laugh when they hear us speaking because we probably sound like 2 year olds, but it's fun. Of course our conversations are only limited to our tiny vocabulary, so we'll never be able to have any in depth conversation about international affairs. I also noticed that when we enter into a shop together, speaking Korean, even in Itaewon, the shopkeepers will automatically speak Korean to us.. even to me. I'm sure they must assume he is Korean at first, but there's no mistaking me for a Korean. Let's hope my Korean keeps improving!