Japan has an extensive public transportation system. Consider getting a Japan Rail (JR) Pass if you plan to travel outside of Tokyo. Japan's bullet trains offer a fast and comfortable way to travel around the country, but make sure to book your tickets in advance to avoid high costs. The metro and bus systems are also efficient and easy to use. Taxis are available but can be pricey, especially in Tokyo.
If you have more time, consider visiting other cities such as Nagasaki, Kanazawa, and Kobe, which offer unique cultural experiences. On the other hand, if you have less time, adjust the itinerary accordingly, but make sure to include Tokyo, Kyoto, and Hiroshima. Keep in mind that Japan is generally safe, but it's a good idea to carry cash as some places don't accept credit cards. Lastly, learn some basic Japanese phrases to make your trip more enjoyable.