The South Bay region of Los Angeles County has a vibrant population of Japanese Americans and Japanese nationals, Torrance in particular (where the store is located).
The South Bay region generally has some old Japanese farming history, because it was one of the few places where non-citizens could own property before World War II. Torrance specifically is where a number of major Japanese companies have chosen to set up their United States headquarters (although some of those companies have relocated in recent years). As a result of all this, the only US city with a higher concentration of ethnic Japanese people than Torrance is Honolulu. This has resulted in market demand for what are essentially recreations of Japanese grocery stores, as well as a number of fantastic Japanese restaurants.
I've found some really cool stuff for sale. Actual wasabi root, sudachi, fresh ogo, luxury fruit (for example: crown melons), etc.