Japanese numbers are simple until you count something. The words for one to ten are quick to learn; the problem is that Japanese attaches a counter to the noun, and the counter changes with the shape of the thing — flat, long, small, bound, alive.

Two counters cover most travel. -tsu for general objects up to nine, and -mei or -nin for people. Say futatsu kudasai for two of something on a counter and you will be understood everywhere. Four and nine are the numbers to watch: read yon and kyuu, because shi and ku sound like death and suffering.