Flight Haneda Airport departs from Tokyo Haneda Airport at 06:25 and arrives at Kagoshima Kagoshima Airport at 08:25.
The flighttime is about 2h 00m. The distance travelled ("as the bird flies"): 1048 Km. So the average speed is roughly 524 Km.
The best day to arrive at Tokyo is Monday and it would be best to avoid Tuesday, as prices are on average 238.57% higher than on Monday. (Average prices, based on 396291 datapoints.)
We have a lot more statistics for flights JL 641 and between Tokyo and Kagoshima.