[Sangetsu]

He's obviously planning on coming to Japan with a WHV, which is good for 6 months.

An open ticket is far more expensive than a standard ticket, so I don't think going with that idea is a good idea. Your best bet is to find a European airline. The exchange rates between Europe and Asia (and Japan in particular) are pretty bad now, so you'll take a little hit if you choose an Asian airline.

The tickets won't be cheap, but at least with a WHV you can get a job in a pub or bar somewhere and earn a little cash during your stay.