Just looked up your flight... 16hrs even!
That's a long flight for Jpn to Germany.
Roughly 25% longer than usual.

But the flight distance was only 7100 miles according to Flightaware.
16-hour westbound flights are usually well over 8000 miles.
This southern routing through China must have some serious disadvantage with respect to jetstream as Alwaysaisle alluded to.