Cousin isn’t incest. Cousins can also legally marry.
I mean youre not wrong, technically, but at the same time, making them childhood friends wouldnt really be different from what I assume the reason is, they were always close. Why do they have to share any blood relation other then to fuel incest fantasies.
Japan literally had to issue a law against portraying sibling incest positively. They got some weird tastes over there and I agree with op why they always gotta bring weird incest subplot into my yuri or really any of it.
Yes im still mad about them doing it in whisper me a love song. great 40 something chapters of top tier Yuri then boom incest subplot.