A very bad Google translation of the Japan military's statement on the incident reads like this:
Now KC-767 aerial refueling aircraft for an emergency landing
Problems occurred in mid-air refueling KC-767 transport plane No. 602, went down today, 16 remain at the refueling boom in the state of Gifu Air Self-Defense Force have landed on the airport.
At the same time as the plane stopped for refueling boom near the tip of an ignition 4 pm 1 minute emergency escape all the crew, fire engines and fire-fighting operations 4 pm 3 minutes to complete extinguishing. The occupant is not unusual.
At present, and no damage to outsiders is a design that is being reviewed for details.
Here's a slightly more helpful statement released by Boeing in English:
Stay tuned for more details.
On Friday December 12 a Japan air self defense forces KC-767J aerial refueling tanker based on Komaki Air Base, Japan, made an emergency landing at Gifu Air Base, Japan. It's our understanding there ere no injuries. The Japan Ministry of Defense has released a statement with details of the incident. We're standing by ready to assist the JASDF when called upon. For any additional details and information, please contact the Japan MOD or JASDF.