Flight International Airport departs from Osaka International Airport at 20:15 and arrives at Tokyo Narita International Airport at 21:25.
The flighttime is about 1h 10m. The distance travelled ("as the bird flies"): 556 Km. So the average speed is roughly 477 Km.
The best day to arrive at Osaka is Sunday and it would be best to avoid Friday, as prices are on average 83.65% higher than on Sunday. (Average prices, based on 409865 datapoints.)
We have a lot more statistics for flights JL 138 and between Osaka and Tokyo.