Well,
After checking quite a few Airlines schedules I cannot see ANY that fly direct to Hiroshima,and that includes JAL
(Japan Airlines) and of course if they don't go direct nobody does!
I looked at JAL's timetables,and to get to Hiroshima you have to change at Tokyo.The interchange(waiting for onward connection) times seem to vary between 2hrs and 5 hrs.
However,why not fly into Tokyo,and then get to Hiroshima (and back)
by the Shinkansen (Bullet Train) and then fly back from Tokyo.Like most rail companies I am sure Japanese Railways offers a great deal on return trips,which may not be much more than a single journey.