I have been to Okayama on the Sinkansen.  But I took the long distance night bus this time, because I wanted to try a different way.  It took about nine (9) hours from Yokohama (I worked in Yokoyama so I took the bus after working.)  to Okayama station.  Every two (2) hours the bus stopped at service stations.  The night bus was going pretty well.  Arriving at Yamako where was my final distination, I took a bath.  Yamako was a spa resort with a theater for Taishu Engeki (popular theater), a ballroom (dance hall), a restaurant and accomodations.  
My two-day-trip made me fun.  I returned to Tokyo by air.  There was a special bus to Okayama airport from Okayama station.  It took about thirty minutes (30 min.).  My flight departed 19:40 was full of passengers and they were mostly office workers.  In these days, some flights are a little cheeper than that of Shinkansen and of course faster.