IŽm by no means a fan of the crappy LH C seat, but I think flying LX to NRT to then exit the airport and then use ground transportation to get to another airport to continue the trip there just to avoid LH C is somewhat over the top.

IŽd just fly LH to KIX, make sure you get a decent seat (you wouldnŽt want to be stuck in a middle seat) and be done with it. I flew LH C FRA-NRT a while ago, and while it wasnŽt as comfortable as the seat on most other airlines I usually fly, I got some 4h-5h of sleep and it was an acceptable experience overall.