Why professional guides?
Professional guides always thinking about guiding guest from all over the world and invest themselves. Also they have a lot of experiences to answer your questions and solve problems. So I recommend you to hire a guide holding the government license.
However, I understand it expensive to hire a professional guide every day 🙂
Free volunteer guides
Here is a volunteer guide group organized by Tokyo government.
Tokyo volunteer guides
Tokyo Volunteer Guides - Travel to Tokyo
Tokyo Volunteer Guides - meet friendly locals. Find out what to do and eat, where to go and stay and more at GO TOKYO. Explore hidden gems even many locals don'...
Your responsibility is paying for transportation, administrations (if any) for yourself and the guide.
Gratuity will be appreciated, I think.