Lan Wangji's mouth opens automatically to Wei Ying's but he cannot stop his hips from flinching away at the first touch of Wei Ying's finger before he forces himself still.

"Instinct," he blurts out, eyes wide as they stare up at Wei Ying's face in apology. "Apologies. Do not stop. I'm sorry." This cannot be arousing for Wei Ying, he thinks. It was so arousing to do this to Wei Ying but Wei Ying was soft and pliant and everything Lan Wangji is not.