I was surprised to find that, unlike all the other Korean cookbooks and online sources I've read, the cookbook "Growing up in a korean kitchen" by Hi Soo Shin Hepinstall uses yuja/yuzu juice (or lemon) in lots of recipes. I've never seen other mentions of yuzu in Korean cooking before (except candied peel or a tea), only in Japanese food so I'm curious to why it's included.
Is using yuzu juice a feature of the author's regional cuisine (she's from Cheongju in Chungchung province)? Is it something most people writing in English about Korean food omit because it's hard to get hold of in the West? Or is it just the preference of the writer?