He doesn't see anything, really. Maybe a ripple under the cloth, but that could be his imagination. And he isn't precisely looking for the tail he knows is there. It's not a source of disgust for him as it is for the unfortunate man it's attached to. For Lan Xichen, the movement just happens to catch his eye, looking down being easier than looking up at anyone and having to have words ready. Oddly enough, he felt happy when Jin Guangyao had allowed him to see the growing tail on the full moon. It felt like he had gotten just a bit closer to seeing him and being trusted again. But now they are back to smiling and showing proper conduct and he is something of a support.

Lan Xichen does smile for the witch when the arrive, bowing politely and giving a warm greeting. He looks at Jin Guangyao when they mention being happy, softly brushing his arm with one hand just for a moment. It might be a bit telling that his expression doesn't change much when the mention of vows comes up. If he looks a bit paler than usual he probably already does from lack of sleep. Any hesitation now will be taken badly.

"No, it's all right," he says. His hand might tremble a little, but it's subtle and he puts it behind his back to still it. "I shall simply say what I am thinking. If you'll forgive my poor words."