This one touch coated in Susa's lifeforce revealed many things about Eri, Susa couldn't obtain solely through her eyes. Like a stream, various information entered Susa's brain to the point it started to hurt. The contact lasted only for a second before Eri threw Susa off and Susa tumbled away on the ground.
There was something. Susa didn't need to touch Eri to figure out. One of Eri's weaknesses was directly related to her scarf-like life force. While it could cut and pierced people, if directly touched it did indeed no harm. On top of that, it actually rendered Eri unable to use her scarf as long as someone directly grabbed it.
As long as Susa took Eri's scarf occupied she could harm Eri, but if Susa forcefully removed the scarf from Eri, the latter was able to get a new one out of her lifeforce and the other one would disappear.
