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You dont necessarily have to read "for your love" to understand this manhwa.
Noona is the way younger guys address females a few years older than them so basically: Noona = older females (any older female that is related or not related to the younger guy)
Also the ML (Yuri --> the black haired guy) is not related to his Noona she is either adopted or his cousin or his dads friends daughter
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I didn't read the other series before reading this one; no regrets. It has seriously dubious consent, which to anyone who reads BL comics is like breathing air, but the characters have enough nuance and relatability that makes it an endearing read, and it's also very romantic by the end of it. Not a positive depiction of healthy relationships for real life, but as simple escapism it was awesome. I wanna reread it when they finish uploading the mature official chapters.
Should I read it?
I see it's a spin-off.... Do I have to read the first one before this?
And is noona his related sister or is it just the formal way they address ppl in Korean ?