The Jeju Provincial Police Agency is different from general police agencies...

‌The Commissioner of the Jeju Provincial Police Agency holds the rank of Senior Superintendent; in short, they are one rank lower than the commissioners of metropolitan or provincial agencies like Daegu, Gyeongbuk, Daejeon, or Ulsan.
Also, because it was previously mentioned that they perform policing focused on tourism, their investigations or criminal cases may differ somewhat from general police agencies.
They even recruit police officers specializing in foreign languages; they are, quite literally, local autonomous police...