One possibility, of course. Or to protect Yancai from what's happened. If they have any sway at all over the dead, that is.

[ He'd opt for it being a protective measure, considering they keep going back in time. They appear to be running away, in his approximation. And why not, considering what's happened as the dead continue to rise from the water.

He's more curious than anything and of course, has no desire to do anything at all with the dead other than take note of what they've seen. ]