Why does Yamasa advise that “hyoujungo” be learnt before regional dialects?
This is for the simple reason that with hyoujungo (standard Japanese), you can communicate with any Japanese person in all parts of Japan, and all Japanese people will be able to understand you. Whilst regional dialects will enable you to ‘blend-in’ better with Japanese people in a certain region, it is highly recommended that you learn and master hyoujungo first.