This database lists almost 400 language schools throughout Japan. Most schools are private language institutions, but some are attached to universities, colleges, and technical training schools or are affiliated with an organization. You can use the database to search for Japanese language schools in Japan and, for Tokyo, areas within the metropolis e.g. Shinjuku, Shibuya.
You can filter the schools by a range of other criteria including course type, study purposes, accommodation arrangements, and nationalities of other students.