Sad news: Kumamoto airport ranks second to last of Japanese ports welcoming international passengers to Kyushu. At 2.2%, it just edged out Nagasaki port's 1.8%, a margin which statisticians refer to as a "smidgen."
Glad news: There is plenty of room for growth! Plans are afoot (alight?) to vastly expand international flights with the pending privatization of the airport. (The below graph includes all points of entry for non-Japanese visiting Kyushu, including sea ports.) - William