There are a great variety of jobs in English education. Besides general English conversation schools, there are jobs available in educational institutions from nursery schools to universities. Curriculum, teaching methods, and teaching materials may need to be adjusted to be appropriate for the age and/or level of the students you are teaching.
In classes for small children (in nursery schools, etc), Japanese is often required for communication. In some cases, even a base level of literacy in Japanese is required in such positions.
While there are full-time positions at English conversation schools, there are also part-time and contract positions available. In many cases, you may be required to merely teach a certain number of classes in a day. At English conversation schools geared toward junior high and high school students, you may be required to teach from the evening into the night.
Those who can speak conversational Japanese
Those who want to work only in the morning or the afternoon
Those who want to have multiple jobs.