I'll soon be traveling to CGK from BOS... I have some miles to use, so of course, I had to go for F or J class. I got F both ways!
BOS>DFW (AA) >NRT (AA) >(overnite)>CGK (JL)
CGK>HKG (CX/J) >JFK (CX) >BOS (AA)

I don't mind the overnight, I've never been to Tokyo, so it would be exciting to see it. The question is: should I try to re-route me through JFK or ORD and take JL F all the way? Or is it worth it to do AA and be able to compare them all? - a TR is promised!

Note that - luckily - NRT>CGK uses first class suites!!