In my experience at this port, ATC clear aircraft to land almost as soon as departing traffic has begun their take off roll. There is then a period of contradiction during the approach when you've been cleared to land but it would be questionable to land until you are certain the departing traffic is airborne. I strongly suspect the landing aircraft in this incident had already been cleared to land and was subsequently told to go-around but either missed the go-around call or dis-regarded it. ATC speak English with a very thick accent and can be very difficult to understand at Naha.