Hello guys, you see, I have a doubt about Sister Yami. It's seems to be the only sister you can't save, because she sais the color is poison, so when you try to use color on her, you kill her. So, it's really the only sister you can't save?.
Thanks in advance.

You can save any of the sisters, Yani included.

You need to use her prefered colours to open her hears like any other normal sister.

Listen out for the sounds when you move your cursor over the colours on the left of the screen. A snake rattle means it's poison for the Sister. Nothing means it's neutral. A sort of warm sound means it's one of her colours.