Thanks guys for the replies. If I had to fly HKG-NRT-HKG is Sapporo still doable? What will be the disadvantage of this route?

I was thinking either NRT -> CTS and spend 2 nights or so there and then fly back to NRT and work myself southwards and then back to NRT with the bullet train and then NRT->HKG. The other method i was thinking was arrive at NRT and work southwards and then fly from KIX->CTS->NRT??? I will be using 2 sector japan oneworld airpass I guess since CX is oneworld.

Thanks,
K.