Japan trip

I wouldn't say 2 days in Hiroshima is too much at all. Everyone thinks of Miyajima, which I also love, but there is more there also. If you want some scenery and to escape the heat, there is always Sandankyo. It is about a 75 minute bus ride from HIroshima Station and makes a nice diversion.
https://visithiroshima.net/plan_your_trip/tour_plans/sandankyo.html

Also much further to get to, but worth the effort, is the Sera Kogen Farm for its magnificent summer flowers.
https://visithiroshima.net/things_to_do/attractions/parks_and_gardens/...

I see that you only have one day in Nara and assuming you're visiting all the typical attractions in the City. As it is the mid-summer you will be arriving in Japan, maybe you can have some fun in the valley of Nara to cool down.
You can do canyoning in Yoshino district in Nara. They can arrange to pick you up from the closest station. This article as a bit more info.
https://visitjapan-vegetarian.com/yoshino-district-nara-japan/#Canyoni...