Misawa this time of year is friggin' cold. My Navy squadron used to fly in there.
Anyway, depending on how long you will be there, and how much traveling you will do, it may be worthwhile to get a
Japan Rail Pass.
For example, a 7-day rail pass, which includes the Shinkansen (bullet train), is 37,800 yen (about $320).
This article, dated last Spring, implies that a round trip from Tokyo to Hachinohe (closet station to Misawa) runs about 30,000 yen, so the rail pass may be a good option. You can use it for other trips, etc.
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