Yeah, I was wondering that myself. I feel like it’s a post bodyswap gift, because Kougetsu knows it’s from the Kin clan. If it was pre-bodyswap then she probably wouldn’t have known where it came from. But I see your train of thought… maybe Reirin sickness is because of a curse and not a weak constitution. So on that note, maybe the Kin clan has been constantly giving Reirin these “gifts”.