How much does an English-speaking tour guide service usually cost in Japan?

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).

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

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.

Sure, if you would like. With highly developed transport, extremely safe, and easy communicate, you are free and easy to do it on your own.

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

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:

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

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)

A full private tour model (car, driver & tour guide) is the best way to experience Japan with a professional guide! But the rate is expensive, especially for small size group. It is recommended to the people who are not budget or big group over 10 persons.