Literally why are they even having this discussion. A moment ago, Lan Wangji wanted nothing more than for Wei Ying to forget the Yin Iron existed. Now he finds himself annoyed at Wei Ying for taking it so lightly and already disregarding the matter.

"I said nothing about raising them. They do not need to be raised."

Wei Wuxian gasps. "Not in front of their little bunny ears, Lan Zhan, you'll make them so sad! Aiyah, how can you just announce to our children that you are abandoning them like that? They will think -"

"Ridiculous." He starts to stride away through the icy waters, towing Wei Ying along by the headband that still joined their wrists. "Worry about the rabbits when things are safe."

They stumble through the magical ward out into the back hill, and everything is suddenly much brighter. To Wei Wuxian's shock and Wangji's displeasure, the sun is already up and in the west.

Jiang Cheng has not seen Wei Wuxian all day. 

Even stranger, Lan Wangji has managed to miss the first day of classes!  

How?  

This happened before, he remembers.  Them vanishing together.  It was supposed to happen later than this, though.  

Once class is over and the students are finally allowed to join in the search, he immediately seeks out Wen Qing and Wen Ning.  

"Do you know anything about Wei Wuxian and Lan Wangji?"

"No. Cloud Recesses is not so large... it is strange that it's so difficult to find them. You don't have any ideas where they are?"

Wen Ning has no ideas about where they could be, which he feels very bad about. The main thing he can do to be useful right now is remember things, but now he can't even remember anything helpful to find Master Wei.

He remembers looking for the pair, but not on the first day of classes. There had been some sort of shockwave that disturbed his spiritual cognition. That hasn't happened yet today; he doesn't know if it's a good or bad sign. He doesn't remember where exactly Lan Wangji and Master Wei had been found, only that they'd both returned unharmed.

"I might.  I was the one to find them last time they vanished.  Checking there again sounds like a good idea.

"It's strange that it happened this early, instead of when it was supposed to.  I don't think anything we changed would have caused it."

Then again, he isn't sure why they vanished the first time.  

"I, couldn't think of anything either. But if it's not us... what else could be different?"

"Hey! Jiang Cheng!"

And just like that, look who's here bounding up the path. Lan Wangji trails behind him, his headband neatly on his forehead where it belongs, the Yin Iron hidden carefully in his robes.

"Jiang Cheng, you won't believe what a day I've had. Did I miss class? Has Lan Qiren kicked me out, yet? Was Shijie - oh, hi Lady Weng, Young Master Wen. You two know Jiang Cheng?"

"Yes you missed class!  You were gone all day!  What were you even doing?"

"Everyone is searching for both of you. We are recently acquainted with your brother, because of the search."

"Well, you're not going to believe how hard it's been! This morning Lan Zhan and I were just going for a walk, and I was trying to find some of the cute beetles I saw with Nie-xiong yesterday by the riverbank when the river flared up for absolutely no reason! Just out of nowhere like it was flooding, it carried us all the way down the mountain, Jiang Cheng. And then we had to climb all the way back up for no reason at all, it was so unfair."

She glances at Jiang Cheng to see if he seems to accept this explanation. "I heard a vague rumor of water spirits causing trouble down the mountain. Nobody mentioned flooding."

"You were on a walk with Lan Wangji."

And just happened to be returning via the most direct path to the cliff he had found them near last time this happened.  

"What made you decide to do that?"  -when you didn't do it the first day of class in my memories?  What was the change?

"I was just looking around. Yknow, Jiang Cheng? How you and me and Nie-xiong and Lan Zhan were all going to look around?" He raises his eyebrows significantly. It is really very dumb for Jiang Cheng to try to get Wei Wuxian to talk about their counter-Wen spying operation in front of the Wen spies. Wei Wuxian will have to make fun of him later.

"Master Wei, did... did the water ghosts get you? Are you okay?"

...huh.

The mention of water ghosts alone would hardly be grounds for suspicion, when Lady Qing had just mentioned rumors, but it's that paired with the concern that makes Wangji almost positive that he isn't the only time traveler here. This is Wen Ning's puppy-devotion to Wei Ying that Wangji remembers, but he doesn't think that developed before Wei Ying saved Wen Ning's life. Certainly it hadn't developed before they even interacted, which up until now in this present they had not.

The very real possibility that this Wen Ning might be Wen Ning, the Wen Ning who suffered and died and then died again, the Wen Ning who stayed by Wei Ying's side when Lan Wangji would not - that's a lot to process. Wangji tries to package away the information for later.

Aw. What a sweet kid. "I'm fine, Young Master Wen. I'm sure those ghosts tried, but a few tiny water ghosts are no match for me and our Lan-er gongzi. Jiang Cheng and I have gotten rid of tons of ghosts together before! They don't scare me at all. These ones must have gotten scared and run away once we were down the mountain. I'm just very tired." He pouts at his brother. "Ai, Jiang Cheng, you might have to carry me. My poor legs..."

He does vaguely remember water ghosts at around this time.  Maybe it was just a matter of a subtle change in Jiang Cheng's behavior causing Wei Wuxian to pass through a walkway a few seconds early or later than normal.  It is true that his brother would follow Lan Wangji.  Inexplicable.  The man is as uninteresting as a rock.  But it isn't strange for him.  

"Go back inside, both of you.  Zewu Jun was looking everywhere for you, Lan Wangji," he says.  "Don't make your brother worry about you."

"And A-Jie was worried too," he says, looking at Wei Wuxian.  The memory of her, running through a battlefield to try and find Wei Wuxian.  Shouting for him, oblivious to the danger.  "Stay where you're supposed to and don't make people have to search for you."

Lan Wangji does not appreciate Jiang Wanyin ordering him around, as though Jiang Wanyin has any authority over him or as though Wangji would acknowledge it even if he did. Wangji looks back at him very coldly.

"I didn't mean to make Shijie worry, Jiang Cheng, really. I wouldn't do it on purpose."

Sigh. "If you really got swept all the way down the mountain, you should let me take a look at you before you go in."

He raises his eyebrows. "Oh? If you wanted to get a look at me you could have just asked, Wen-guniang. I'm probably much more exciting than whatever else you're looking f- ai, Lan Zhan! Where are you going?"