Higurashi no Naku Koro ni Rei - Irotoutoshi-hen - Vol. 4 Ch. 18.6 - Extra

[MangaDex]

 

[KensouADV]

Pretty fun chapter but what hell Rika? You know she's Mion's daughter, not Shion right? Also, I find it a bit weird they're calling Rika as "big sis/onee-chan" and not treat her like their aunt, specially Sakiko. Maybe it's a cultural thing.
Thanks for the translations.

 

[Lunkli]

Also, I find it a bit weird they're calling Rika as "big sis/onee-chan" and not treat her like their aunt, specially Sakiko.

It was shown in earlier parts of the story that Rika doesn't like being called "Aunt," so even though that's what most of them instinctually call her, they make sure to call her "Big Sis" when speaking to her. As for referring to non-family members as though you're their sibling, that's a cultural thing. It's fairly common in east Asian cultures. People do it in China, Japan, Korea, Indonesia, &c. It's a way to be nice and familiar with someone without being too familiar.