yes, there is a cursory immigration process. Follow the signs for international connections. We did this last in June, and while the process itself doesn’t take long, if at a peak time, there can be lines to get through this process. We transited to NRT - something like late morning, and they were metering folks into the customs hall, which took a whole, I think we waited about 25 or 30 minutes to get through.

You’ll have to go to a kiosk, then hand the receipt, as well as show both inbound and outbound BPs before you will be able to go back into the departure hall. The requirement to show the inbound BP makes no sense to me (how else would I be in that area if I didn’t come in from somewhere else) and was not mentioned before we were asked, so perhaps that is part of the reason the line was longer…it took me a bit to dig those out. You won’t see bags, and no security to go through. For us, we had a 2 hour connection and barely made boarding on time, though our 7 and 4yo were with us which slowed us down some.

Note: if doing the reverse, and connecting back to the US, you do need to do US Pre-clearance and security, and they will verify the number of bags checked in that process. But you won’t see your bags that way either (unless CBP wants to pull it for a search).