I did check out the characters section since I was curious about Sara's "condition". It said that it something the women in their family have. What exactly do they have?
It starts when they experience puberty("3 years ago" in terms of the game timeline) and is genetic, passing down through the ladies in the family. I didn't base it on any specific thing, haha. The CG that you see at the end of ending 1, all the details in it? That's all I wanted to go for in the design of what the 'condition' is. c: