Post 400 messages on a Tokyo related forum, it should be around $30 .. $50 (between $0,07 and 0,12 each message, depending on the quality of the work).
A good work means having a GOOD SEO in mind when posting GOOD AND USEFUL CONTENT.
The title of the discussions should be similar to common keywords, don't write about things that nobody would search about.
Write everything about what people is searching, related to Tokyo.
Don't copy content from somewhere else.