In addition to teaching I am also registered with several Mystery Shopping companies. Do you know what Mystery Shopping is? Go on over to Wikipedia and read all about it.
It's free to register (in fact you should never register where you have to pay!). I receive email on a regular basis alerting me to the jobs available in my area. It's up to me whether I apply for them. There are quite a few jobs for Japan. I have "shopped" in fashion stores, and reviewed a few services. It's a lot of fun because you get paid to shop.
Do your own research:
Corporate Research International
International Service Check
When I got paid the first time I felt really empowered. It was the first income outside of teaching that I had had in Japan. It opened up a whole new world of possibilities to me.