No problem, enjoy your trip. Don't forget there is half country south of you that you are not seeing.
Okayama is close by and it is famous for its nice castle, plus Korakuen, one of Japan's Top 3, and also the beautiful Handayama Garden. If you'd like to get off the beaten path for a while, the half day hike up to Konpirasan in Kotohira, Kagawa, is marvelous. Going to Takamatsu is also great - it has one of Japan's finest gardens also, called Ritsurin.
Hiroshima also has several good places. Miyajima is naturally the most famous, and aside from Hiroshima itself, Onomichi with its temple tour and Kosanji Temple is spectacular. Just beyond Miyajima also lies Iwakuni with its historical bridge and castle on top of the mountain. Taikodani is also a beautiful shrine in Tsuwano, Shimane.
Hagi Castle was actually delightful, and the preserved samurai district and Mori related temples a rarity. One of the very best is the Akiyoshi Limestone Cave, a 300 million year old wonder with huge caverns and underground river running through it.
If you can, try to find a little time to see the Japanese themselves. Go visit a Japanese supermarket and see what people typically eat. Look through a park and watch the Japanese kids play. Learn about the history of some of the places you visit before your departure - it will give your trip so much more meaning.
You will find a lot more to explore and enjoy.