Firstly, apologies for asking a question that may well be better placed at kiddiestalkingaboutairlplanes.net.

Secondly, perhaps this would be more appropriately placed in the JAL forum, but I think this forum has a wider audience and more likely to get an answer.

Looking at the schedules, NRT-DEL-NRT is non stop yet the outbound dayflight has a 10:00 scheduled flight time. The return overnight flight only has a scheduled duration of 07:25.

What is the reasoning for such a difference in duration for a sub-4000 mile flight?

I initially thought it maybe due to crossing restricted airspaces, but that doesn't explain the shorter return leg. Winds could be another reason, but surely not that favourable?