Search engine marketing for organic results is very time-consuming, but can be done. With a site like yours, however, a paid campaign would probably be more effective because you can target a few key words and steer traffic directly to your site. Most of the sites about teaching in Japan that I know have paid advertising, though I only know the ones that are directed at teachers there like GaijinPot. I have added a link to your site here:
http://www.usingenglish.com/links/Tutorials/