Suixun, as the name suggests, means wandering and tracing.
What made her life go to the point of no return?
What separated these two closely related sisters?
What caused the originally close brothers and sisters to turn against each other overnight?
A key and a mirror that fell out of an old and unopenable book brought a pair of half-sisters separated from each other into a mysterious destiny.
They travel through different time and space just to find something lost in the past, but they must pay a corresponding price.
Maybe it's experience
Maybe it's training
It is undeniable that these may be tests in the dark...