Great advice above. If you aren't tied to Hiroshima, consider spending some time in Kyushu (the big island south of Hiroshima) and/or Kyoto/Osaka/Kobe/Nara. Both areas are in easy shinkansen (bullet train) reach of Hiroshima.

Also, on the low end for food, you can spend a few hundred yen in conbini (convenience stores, like US 7-11 on steroids) or street food and fill up easily. But you'd be doing yourself a disservice to eat every single meal like that.