The highest demand for business English instructors is in Tokyo, since this is where most of the companies are located. The High School Teacher English is a part of the high school curriculum in Japan. Although all high school students study English, the emphasis is on reading and writing. It is often the case that most Japanese teachers of English can't speak English at all. The Japanese government-sponsored JET program hires over 2,000 native English speakers every year to teach in Japanese high schools.
Many universities hire English teachers for their foreign language faculties.
Working conditions and salaries are comparable to their Western counterparts. See the Universities page for more information about working in the Japanese university system. A lot of conversation schools only ask for a university degree. Schools, however, will generally favor those with qualifications and experience than those who don't. A post-graduate level qualification is considered the minimum for a university teaching position.