The large eikaiwa like Geos, Nova and Aeon seem to recruit all the time and have quite a high turnover. It shouldn't be too difficult to get a job without experience- the idea behind Nova and Aeon is that the lessons are very standardised and formulaic so that if one teacher goes another can belnd in seamlessly. If I were you, I'd check out the forums at gaijinpot.com and letsjapan.org, though do a few searches first for the names of schools and things before posting- they can get a bit crabby when asked the same question for the thousandth time, but they are both fairly active and have people who know the country inside out.
I'd also check out any of the smaller schools on ESL Blacklist sites like englishschoolwatch.org as I have heard of some dodgy places.
- For Teachers