It sounds like this ROK C-130 was in contact with U.S. Air Force air traffic control to land at Kadena, but no one bothered to inform the Japanese Air Self Defense Force (JASDF) of this landing:

Japanese fighter jets intercepted a South Korean airlifter low on fuel that entered Japanese airspace without approval while diverting to Kadena Air Base on Okinawa, officials from both countries said Friday. A South Korean C-130 Hercules entered Japanese airspace without approval on July 13, a spokesman for Japan’s Joint Staff said by phone Friday. It was en route to Andersen Air Force base, Guam, to participate in a multinational exercise, according to text messages sent to reporters by South Korea’s Ministry of National Defense.
The ministry did not name the exercise, but the U.S. Air Force is conducting the large-scale Resolute Force Pacific through Aug. 8 across the Indo-Pacific, including Guam. The C-130 burned more fuel than anticipated while rerouting around stormy weather and diverted to Kadena to refuel, according to the ministry. However, the diversion was made without prior clearance from Japanese authorities, the Joint Staff spokesman said.
The Japan Air Self-Defense Force scrambled jets to intercept the C-130, but the spokesman did not provide further details. “We transmitted to South Korea that this scramble is regrettable and asked them to take measures to prevent further instances,” he said. “But as they are our important partner, we will continue to work closely together to address the issue.”
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