Amused Bicycle Sellers

Today we bought bicycles. The man in the shop spoke only Japanese. We managed to buy 2 bikes and get the man to attached kid's seat on another with our unexisting Japanese. A younger guy came to help after a while. He spoke english and he started translating. When the older guy was working on a bike, the younger guy asked him something and got an answer "Nihongo" (japanese). By their amusement I guessed that the younger guy asked what language we used before he came. I too thought it was funny but I didn't tell them.