Originally Posted by JALPak

The OP is connecting to a JAL international flight not domestic.

It depends on whether your domestic flight is really a domestic one. JAL operates a number of "domestic" flights that are actually regarded as international ones. So if your flight is one of them, you don't have to go through immigrationa and custom procedures at NRT. Only need to go through security check point and re-enter airside. Otherwise, you will have to pick up your bags, go through custom, then check in again. The real domestic and international flights have different airsides. So you won't be using the Sakura/F lounges for the international flights. There are separate ones for domestic flights.

For your return flight, assuming it's a real JAL domestic flight, here is the procedures.