Apologies for the late reply. To be honest, I usually tire myself out by taking extra steps at the airport prior to any flight, especially these red eye flights. Whether in Y or J, usually I can sleep for 3-4 hours immediately after take-off.

There is a small snack service that takes a prolonged period of time to complete. I suggest to have an eye mask and noise cancellation headphones (very useful if in Y). Indeed, the full meal service does start about 3 hours prior to landing. Why JAL does this is somewhat irritating, as other oneworld airlines like CX and AA can dash out their meal services in under 2 hours. The service is also done via 1 tray serving, which in theory, can mean that the meal service can be done in shorter period of time.

You can choose to deny the meal service and try to maximize the sleep on the 7 hour flight. However, if you are sensitive to light and noise, this is not guaranteed. If you have to work or start your touring immediately at NRT, skip the meals and prepare the best possible to sleep as much as possible.

MH has a similar meal structure on this route (likely NH as well). Although JAL food is decent; nothing can beat a nice rest.

There is MH 70, a daytime KUL-NRT route that you can take if this works for you (I see this option as a JAL codeshare if I search for flights originating at KUL).