Either direction I always eat and drink through the 1st service and then try and sleep as much as possible. 4-5 hours is great. Then arrive in Japan, dinner, drinks and stay up until midnight. Then another 4-5 hours and you're good to go.
This strategy works well. I get tired in the afternoon, but usually catch a second wind in the evenings.

It also helps if you're not used to getting a lot of sleep to begin with

-Scho