Hiroshima to Tottori

Hello there,

The train can be boarded using the JR Pass but there is an extra charge. You can also take an alternative route via Okayama without paying extra. It just adds additional travel time.

Takeshi over at JPRail did a very good write up about this:
http://jprail.com/trains/sort-by-departure-arrival-stations/stations-in-chugoku-and-shikoku/okayama-sort-by-departure-arrival-stations/the-fastest-train-access-to-tottori-from-okayama-limited-express-super-inaba.html