Wei Wuxian is holding out his hand for Lan Wangji to hold and his face bluescreens for a second. Because - hadn't he also said that he could practice flirting and kissing? Hadn't he just offered those things?

Was this Wei Ying trying to slyly clue him in on something? Was he, perhaps, shy, and thinking that Lan Wangji for some reason, likes girls?

He does keep mentioning the girls.

But for all these actually not-dumb thoughts, he is too busy currently thinking with his heart instead of his head, and so, he slots a hand into Wei Ying's hand, and holds on tightly, and looks him dead in the eyes as the two main characters finally get over themselves and walk down the altar.

He thinks of something romantic to say. What is something he could plausibly say to Wei Ying but also a girl?

With his straight stare, he says: "I wish to night-hunt with you."