Donald Keene sounds mystified in his autobiography, even after 60 years of dealings with the Japanese:
“Japanese, even taxi drivers who clearly have no intention of inviting me to dinner, often start a conversation by asking what Japanese food I dislike. (Nobody ever asks what Japanese food I like.) They are particularly eager to know whether I can eat sashimi (raw fish. When I say that I am fond of sashimi, they seem disappointed, but they persist, asking next about natto (fermented soybeans), and if I say I eat natto, they ask in desperation if I eat shiokara (salted fish guts).” Chronicles of My Life pg 11
I’m afraid I see something unpleasantly nationalistic in it, as if they wish to hear that no one else could ever become Japanese as hard as they might try.