The Genealogy of Bun-Bun

After closing the shop, I was chatting with the staff when Hayashi-san, a part-timer, started saying something I didn't understand about buying things at 'Bun-Bun'.
“Bun-Bun? What’s that?”
“You know, 7-Eleven. Don’t you call it that?”
“That’s the first time I’ve heard that.”
“They call it that in Yokohama.”
Hayashi-san used to be a hairdresser, but before that, she was a punk and apparently played with the famous band guitarist [Name] [Name]. If that’s the case, then [Name] [Name] must have called it Bun-Bun too.
I was satisfied with that explanation, but Saito-kun, a part-timer, chimed in with strange intensity.
“They don’t say that in Yokohama.”
“They say it in Yōkōdai.”
The range of 'Bun-Bun' seemed to shrink suddenly from the entire Yokohama area.
“I’m from Yōkōdai too, and I’ve never heard it.”
Saito-kun’s pursuit was quite persistent.
“Eh! So, is it just around me?”
Hayashi-san’s 'Bun-Bun' territory was reduced in the blink of an eye to just the few people around her.
“I guess so.”
Saito-kun stopped his attack there, but Hayashi-san looked quite shocked and was laughing sheepishly. If this were Chibi Maruko-chan, she would be turning white with those strange horizontal lines across her face.
I felt so sorry for her, and since it was used around her, [Name] [Name] must have said it too, so I decided that I would inherit the 'Bun-Bun'.

When I told that story during a store manager meeting, everyone said they didn't know 'Bun-Bun' either. Only Kitajima-san found it amusing and kept using it for a while afterward.
However, while the version I heard from Hayashi-san had the same pitch for all the syllables—'Bun-Bun'—Kitajima-san’s version went down in pitch—'Bun-Bun'—so strictly speaking, they are different schools. It’s a sub-school. Still, it’s better than the genealogy dying out completely.
Kitajima-san quit a year before I did, so I don’t know if she kept using it after that.
I have since moved my base to Osaka and Nagoya, and I continue to use 'Bun-Bun' wherever I go, but unfortunately, it seems no new users have been born.