If you can get PY paid for, I would suggest taking Cathay Pacific or Singapore. Connecting in Japan or Korea means you will probably be stuck in regular economy class for the intra-Asia legs, which will be long flights (5-7 hours, possibly overnight). With Cathay or Singapore you have better chance of getting PY the whole way, and even if you don't, the intra-Asia legs will be only 2 hours or so.