JRPass

Hi there,

The difference in price between a 7 and 21 day pass is ¥29,400, so in order for a 21 day pass to be worthwhile over a 7day+tickets you'll need to spend more than this difference in the ticket portion of your trip. Lets take a look at those costs:

1. Sendai(miyagi/jr) > Ishinomaki: ¥3580, (123mins, 80km)
2. Ishinomaki > Sendai(miyagi/jr): ¥1280, (97mins, 71km)
3. Sendai(miyagi/jr) > Tokyo: ¥10590, (102mins, 351km)
4. Tokyo > Ishinomaki: ¥12150, (242mins, 422km)

TOTAL: ¥27600 for 4 legs

As you can see the ticket costs will just come under the difference in cost between the 7 and 21 day pass, with a saving of ¥1800. In my opinion its worth taking the 21 day pass option just to ensure you have travel flexibility for the period 9-20, however it will very much depend on how firm your plans are.

Hope this helps!