Yeah, local supermarkets and bookstores are always great places to try. Experiencing local prepackaged foods with different standards of bare minimums than yours and flipping magazines for topics you're familiar in unfamiliar language and formats is not an easy moment to replicate at home.

> It's 10:00 in a Tokyo 7-Eleven, ... , katsu curry buns, ...

nitpick: "katsu curry" means katsu plus curry. katsu means Japanese localized cutlet fries. curry means curry. there are katsu sandwitches and curry buns in 7-11 JP, but no katsu && curry bun in 7-11 JP. Calling curry buns katsu curry buns is same as referring to french fries as fish and chips with emphasis on FISH when there isn't in the bag; it would be a false advertisement if a restaurant had done it. The author need to make up their mind and call it Japanese curry, or if their style guide prohibits it, just curry without indicating what type of it is, or, Japanese curry is not supposed to be much different from the Royal Navy recipe anyway, so you could call it the Navy style, that's probably fine too.