You don't give enough info, such as the total number of days of your trip, or how long you will spend in Hiroshima. If you leave Hamamatsu for Hiroshima and return to Tokyo within a week, a 7 day Pass would pay off quite handsomely. If you were thinking of getting a 2 week pass, it is more murky. If you started using your pass from Tokyo to Hiroshima and back, you would be barely able to recover the costs. If from Narita Airport and returned to Narita on the Narita Express Train within 2 weeks, that would help even more.