Get the cheaper roundtrip ticket from Finland to Japan but book the return segment on a high travel day where you have a high probability of being bumped. And then go to the airport and try to get compensation.
Originally Posted by
phillipas
What make even more sense is to find a cheap single that is cheaper than a return which shouldn't be that hard to do - try expedia, etc if Finnair's own site doesn't throw up anything helpful (which at a quick glance it doesn't seem to).