CO does not have the 5th freedom right to fly beyond Japan for connecting service, and it wouldn't necessarily make sense for them to do so at this time.

On the other hand, CO does have a subsidiary (Continental Micronesia) based in GUM which offers a pretty extensive intra-Asia network, albeit not daily service and it's almost impossible to connect.

Regarding the allocation of seats, as far as the agreement between NW and CO is concerned, CO has access to book in all NW seats.