[sarasi]

spicytuna is correct- for unskilled foreigners (although of course there are skilled teachers here as well), English teaching is by far the most common job, however it is more or less restricted to native speakers.

Other fields which have a lot of foreign workers are IT and finance, but those jobs require previous experience as well as good Japanese skills.

There are also a lot of foreign bar hostesses here, but a large number of those are here illegally.

Japan is not a country of immigrants like Brazil, the US or Australia for example, therefore it's not that easy to come here to work unless you're a native English speaker with a degree.