I had not picked up on this before, but this letter makes it clear that MB did not just transit in Seoul/Tokyo as she said 'a most interesting visit to the east', which def suggests a longer stay..although odd that she did not elaborate. Also the fact that she mentioned manhandling her luggage, which, if she had a through ticket, could have been checked to her final destination.This is the transcript (sorry a few misspellings) of the letter to Sally. I’ve removed the final paragraph as there is some personal info on there.
Marion did send more postcards to other family members & friends but sadly these were destroyed before it became apparent she was missing.
Not proven obvs, but links nicely to RB using JAL imo.
Thank you for the transcripts as my eyesight isn't what it was...