To add to the artist's explanation, apparently "Sorry Curry" was created to commemorate that the surname "Yamaguchi" was ranked first in a list of surnames that are the same as prefectural capitals, and that it's "Sorry Curry" as a way to say "I'm sorry only Yamaguchi-san and people from the Yamaguchi prefecture can buy this" (Source).
I have no words, this must be one of the most confusing publicity stunts I've ever heard of.