These are the Japanese words which from my experience are most common in conversations between two English speakers who have been in Japan for a fair while:
Some are quite easy to explain. For example, “apaato” and “manshon” aren’t strictly translatable into Japanese, and rice ball is a horribly clumsy expression for “onigiri”. “Konbini” is probably a combination of being easier to say than “convenience store” and the stores seeming somehow different to and/ or more common than those back home. Why “keitai”, though? It does seem to be the same with use of the word “handy” for English-speaking people in Germany, so maybe it’s something to do with the switchover happening while many of the expats who set the trend already being in the country.