[Sangetsu]

Technically, you do not need a bachelors degree to teach in Japan. What you do need to qualify for a visa is three consecutive (and verifiable) years of teaching experience, and 12 years of education in the country who's language you wish to teach.

You will not be able to apply for a teaching job from overseas without a degree, you'll have to come to Japan and convince a school to hire you. Some are aware that they can sponsor and hire a person who doesn't have a degree (provided they meet the above mentioned requirements), but most won't.

To verify your experience, you'll either need to bring pay stubs, tax records, or certified/notarized copies of a labor contract/s from your former employer/s.

Bring the above mentioned paperwork, a signed sponsorship application from your employer, and passport photos (as well as your passport) to the immigration office.

You'll need to make a good impression with whichever school you are applying to, it's not particularly hard to find teachers who possess a degree, so you'll have to convince them as to why they should hire you over someone who has a degree.