As you mentioned, tipping isn’t accepted in Japan. It can even be considered rude. As to the situation, you can thank the book store clearly and all you can do is leave them the best review you can.

Airbnb provides some guidance on this:

Should I tip my experience host?

It's up to you. Your host set a price they expect will fully cover your experience. We suggest you research cultural hospitality norms in your destination. If you want to show appreciation for your host, write a review encouraging other guests to book their trip.