Hi there,
I'd suggest purchasing a 7-day JR Pass - excluding travel between Hakone and Odawara, it'll cover all of your itinerary. I'd suggest activating it between the 6th to to the 12th, as travel between Osaka and Kansai Airport will be a fairly cheap one-way trip that you'll have to purchase individually compared to the other journeys you'll be making, e.g. to Tokyo and Hiroshima via the Shinkansen trains.
It's also worth looking into a Hakone FreePass - our site does not sell this as the trains that connect Odawara to Hakone are operated privately and not by the JR group. The pass includes the round trip from Odawara to Hakone and back, as well as covering all major transit links within Hakone including sightseeing cruise for Lake Ashinoko, cable cars and local bus travel. More info, as well as a map detailing this, can be found here.
Hope this helps!
Alexis