Originally Posted by nishimark

Yes, you must collect bags after immigration in Haneda and take them to the domestic luggage check-in area. It's very likely that your bags will be waiting for you after you clear the passport control/immigration area. You will have enough time, but likely not enough to shop or get something to eat before moving to domestic departure gates. For return, yes, you will check bags at Itami all the way through to your final destination, with 90 minutes enough time to transfer to international departure. Another note. You will only need to arrive at Itami at about an hour or maybe a bit more for check-in. It's a small airport and very efficient. There is a special check-in area for domestic flights that transfer to international in Tokyo with manned check-in counters.