The yin yang orb was responding to Sanae, not the shards; yes, there's a good likelihood that she's somehow involved, but we don't have anything remotely relevant in character. We haven't had a chance to really interact with Kikuri, so we don't have any definite proof that her half of a shell is anything more than a coincidence. Plus, we don't have any reason to be dramatically suspicious towards her when the one time she was mentioned was when we first came up. Just cool down, and wait a bit before whacking people.