I assume by "combine our itinerary" you mean you want to be on the same PNR.

To be on the same PNR, you have to fly the exact same itinerary. If you booked one-way flights, you could do that for your HKG-NRT-ORD trip, but it would likely cost you lots of money to book everything as one-way trips.

The real question is why you feel it's important to be on the same PNR?