Travel during Obon?

So I'm trying to find time to meet up with a friend of mine, and the only mutually workable time seems to be during the Obon holiday, which they described as "a nightmare" for travel.

I've been to Japan a number of times and speak relatively well, however I've never happened to be there during Obon before.

Is travel a total non-starter, or does it just require extra planning and booking everything well in advance? My route would be from Tokyo to Niigata, then back again on the Shinkansen.