This was my thought exactly - Find out where the candy otakus and/or japanophiles hang out, and test buying advertisement there, in whatever form is available/

This was my thought exactly - Find out where the candy otakus and/or japanophiles hang out, and test buying advertisement there, in whatever form is available/can be negotiated. This might look like banner ads, blog sponsorship, etc. Test and measure what converts to subscriptions, and renew with the ones that work.