At Delta.com, you can book a flight from NRT to LIH, which puts you on a connecting Hawaiian air flight. I'm sure that if the NRT flight was late, you would have no problem getting on a later flight in that situation. I think that it's also cheaper to book all the way to an outer island on Delta, rather than buying separate tickets.

I've been through HNL customs and immigration several times from Japan. If you have an American passport, your line at immigration will be much shorter (go to the right at immigration). If you have Japanese nationals as family members flying with you, they can go through the American passport line with you. I've found HNL to be very efficient as compared to other places. For example, more than once it has taken me less than 90 minutes from touchdown to Waikiki. Two hours should be fine to make your connecting flight.