Flying business class USA to KUL, I arrive NRT (JL) at 4pm and depart HND (MH) at 11:55pm (thanks MH for dropping your NRT flight). That gives me about 8hrs layover
Assuming 3hrs for NRT immigration and Limo bus to HND, I will have 4 hours to kill. From memory there is nothing to see immediately around HND, but what about NRT?
Is it worth heading out to Narita San Sinshoji for a couple of hours, or forget about it and just go straight to HND to wait it out in the lounge?
Depends how much luggage you have.
if minimal, take the train (expensive nex or cheaper Narita sky access via central Tokyo), spend time in central Tokyo before heading to hnd