I would not recommend the NRT transfer. It is possible that there will be substantial rolling blackouts around Tokyo by late June, since it will be hotter and AC usage will be higher. NRT itself has on-site generators so will not be affected, but layover hotels and connecting transportation could be, and airlines may make operational adjustments accordingly. Besides that, many airlines have already been switching equipment to and from Japan and other points in Asia in order to cope with reduced demand at NRT, so you can't really trust any equipment allocations at this point.

Go through ICN and worry about sleeping once you are in FUK. It will be a nicer connection anyway -- you cannot use the good lounges at NRT on an intl->domestic connection, and the NH domestic lounge is pretty crappy even when it's fully operational. Plus you have to claim and re-check luggage if you go through NRT, which is a pain.