Old info but some 13 years ago the ex did the CELTA course over 5 weeks in Oz before heading to Japan - just in case, also no degree etc.
Part time (if any) was only ever the plan, ended up at a private kindergarten/young children school doing about 12 hours a week and enjoyed the experience.
That was down Kyushu way but I'm sure there'll be opportunities around - depending what level/standard you're looking at of course.