On my trip to Kyushu, I used the JR KYUSHU RAIL PASS, and it was really convenient for visiting several cities in one trip! Attractions around Kyushu are relatively far apart, so traveling by JR train saves a lot of time on transfers and buying tickets.
Along the way, you can enjoy the scenery of different parts of Kyushu through the train window, making the train ride itself part of the journey. Especially if your itinerary includes several cities, planning your routes and travel sections in advance makes using the pass easier.
