What possible explanation could there be for these black Q-tips? That they are from Japan should give you half your answer: if there's anything the Japanese know, it's the fine art of sucking goop out of the ear.
core77's answer to the riddle:
Ear wax is yellowish; the high contrast of a black Q-tip shows you exactly how much you're "getting." My friend assures me I will be amazed (horrified is more like it) after using these.
I struggled for a closing quip, and even went to Wikipedia to learn more about ear wax in the hopes I could come up with one, but nothing immediately presented itself. Therefore, I will leave you with this remarkable factoid: "Many species of whale have an annual buildup of earwax, adding one, two, or four layers (depending upon the species) each year. Similar to the incremental dating method of dendrochronology for trees, the number of layers can be counted to determine the age of the whale after its death."