How can one in Japan obtain a National Guide Interpreter qualification certificate?

If you are not an Experienced Traveler or on budget, my answer is yes, a guide is really great value for money and ensure a fantastic tour experience for you.

To be honest, $100 a day is a very limited budget for a trip to Japan. Only suitable for Backpacker Free travelers with apartments stay.

If you plan for a trip to Japan with 5000 USD, you can expect at least a week trip to visit Japan (not luxury style).

Are Japanese tour guides who provide interpretation services required to have a national interpreter guide qualification certificate?

Travel Maps of Japan's Attractions，Distance between cities and required driving time.

The cost of a trip to Japan can vary widely depending on factors like group size, tour time, tour days, travel style, hotel levels etc. However, here's a rough breakdown of costs for an average 10-days Japan land trip for reference only. (international flight exclude, pls check it on your own)

Japan offers a completely different landscape throughout the year. The best month to visit Japan depends on what kind of landscapes you're looking to experience:

In the National Interpreter Guide Examination in Japan, ten foreign languages are offered, including English, French, Spanish, German, Chinese, Italian, Portuguese, Russian, Korean, and Thai

If you come from a non-English-speaking country, the tour guide service in your language must be booked in advance with sufficient time

Eating out in Japan is with widely price range from several dollars to hundred dollars. It's up to you to make it expensive or cheap.