Hi there,
If you are able to fit your travel itinerary (starting from when you leave for Tokyo) into a 7-day period, then I'd certainly suggest purchasing a JR Pass, despite the fact that travel to Hakone is only covered up until Odawara Station. When people include Hakone in their itinerary, I do also separately recommend purchasing a Hakone FreePass, which covers the round trip from Odawara to Hakone and back, as well as all the transport available in Hakone including the sightseeing cruise. More info can be found here as this transport (and pass) is operated and sold by a private railway company.
Kind regards,
Alexis