[ She still only just started, so the constant improvement was really impressive. It really wouldn't be long before Celty was reliably throwing borderlines down, for whatever reason was necessary. ]

There's a thing called ablutions that require the use of them. Other than that... I guess it's just a more reliable thing against ayakashi and spirits? That and most of us don't really have powers, and even less can do what you do. I guess because it's universal among all us shinki, it's also the easiest to learn from others.

I don't really understand it all myself, so I'm not exactly the biggest help.