Japanese humility, or something else?

It trips me out, invariably, whenever I run into one of my former students who've graduated and moved on, one of the first things out of their mouths is "You remember me?" - filled with what can only be described as shock, awe and surprise.  Which always prompts me to respond, albeit in my sad Japanese - "Of course I remember you."

Now, I'll grant that about 80-90% of the time I'm not going to remember their name - because Japanese is hard, and my facility with the language sucks - but of course I remember who they are.  I remember their faces and their personalities, if they liked English, their sense of humor, who their friends were...  I mean, I remember them.

Of course I do.  I don't think I'm ever gonna forget these kids.

Happened again today.  Ran into a former student and her mom out at the grocery store and as soon as I got out the 'hisashiburi' [long time no see] her mom blurts out "You remember her?"  But my student was likewise and obviously surprised I remembered her...  So I did the standard 'of course' and asked her how she was doing and how high school was before we all continued on our merry shopping way.

So I wonder, is it that they don't think they merit or expect being remembered?  Which plays into the Japanese cultural trope of humility.  Or is it they don't expect a gaijin teacher to remember them?  Which plays into a different, somewhat less flattering, Japanese cultural stereotype.  Or something else?

Either way, I'm glad to surprise them in a small way and pop whatever expectation bubble they had, even if just a little bit.