Came across this Minicos (Costco's convenience store-size version of its shops in Japan) in the city of Ureshino (Kyushu) not too far from the train station. It had a fairly wide food selection considering its size, as well as baked goods that looked like something you'd see in a US Costco or Walmart with individual muffins 3- to 4-times larger than what's standard in Japan. Kind of gross just to look at but I guess Japanese consumers are buying them. They also sell some decent natural and organic imported food items at low cost, especially if paid with a US credit card. So far, I've seen these shops in Nagasaki Prefecture (multiple), Oita Prefecture (Beppu), and Saga Prefecture (Ureshino), but there are other Minicos in Kyushu, Honshu, and Hokkaido.

Ureshino Minicos