Stores that sells imported foods (Tohoku region)

Depending on what you are looking for, in Yamagata prefecture you have a few options:

Yamaya - The national chain of liquor stores sells, as one might guess, alcohol from all over the world, bit also sells a lot of import foods. Most of it is nonperishable (pasta, chips, snack, etc.), but they also have some deli meat and cheeses that are a little pricey but delicious.

Gyomu Super - This national chain of restaurant supply stores also frequently has a small business in importing a limited selection of foreign foods. The selection at each location varies, but you can usually find snacks, peanut butter and jelly, some frozen foods, bottled, jarred or canned sauces, vegetables, meat or other goods and occasionally deli meat.

Costco - There is a Costco location in Kaminoyama (a bit south of Yamagata city). It's a touch smaller than your average Costco location in Japan, but still has most everything you might expect.