Bed Intruder

The male lead was forgotten in favour of the villain

"So let me see if I am understanding this clearly," Yu Ziyuan said to Lan Wangji, "Nie Huaisang essentially drugged you so you could drown your sorrows because Wei Wuxian publicly besmirched your Lan honour and then you mistakenly entered A-Cheng's room thinking it was your brother's and was too out of it to realise what you'd done?"

Lan Xichen smiled awkwardly and answered for him.

"That seems to be the case."

Given that Lan Wangji actually had no memory at all of the night (or well, he did remember his 'dream' but he was too ashamed to admit it because clearly that had not been a dream) it meant that the series of events described did not have clear proof; it was more circumstantial evidence than anything.

But they'd gone to Lotus Pier and met with Sect Leader Jiang and his wife and told the whole story, both Nie Huaisang's and Lan Wangji's recollection of the events leading up to the 'attack' and Lan Xichen's realisation the next day.

It really seemed that it was truly Lan Wangji.

If it was Jin Guangshan it would be difficult to explain how he got away so quickly without being seen at all by Wei Wuxian (or anyone else) given that he was drunk and flying his sword to a different part of the Wens' guest quarters.

Also they didn't check to see if Jin Guangshan had any partners in his room at the time of the incident. He very well might have, even if he himself didn't remember.

Jin Guangshan was a sleazeball but he'd been innocent of assaulting Jiang Wanyin apparently.

And even Lan Wangji wasn't trying to assault him. He was aggressively cuddling who he thought was his brother.

But of course Jiang Wanyin was not his brother and it was a horrible mix up so even though no assault was intended, it didn't stop Jiang Wanyin from feeling violated and unsafe.

Jiang Fengmian, in an unprecedented move yet again (in his wife's eyes especially) did not take this as an excuse to brush away the incident or his son, but instead frowned unhappily because Lan Wangji's insistence on owning up to it and asking for punishment meant that they'd have to clear Jin Guangshan of the deed, and quite frankly he didn't want to do that.

Jin Guangshan may not have actually assaulted A-Cheng, but the way he spoke about Jiang Fengmian's family was abhorrent and it meant he'd been thinking about it so what was to stop him acting upon it at some point the way he did with poor Madam Qin? Jiang Yanli had been engaged to Jin Zixuan, if the marriage had happened, who knows what could have befallen his daughter in that man's home. So no, he wasn't happy at all. Lan Wangji may have been the one in A-Cheng's room, but he didn't actually mean to assault A-Cheng, whereas that lecherous turd in the 'dungeon', did.

Lan Xichen was also unhappy because his little brother meant no harm, but even if he didn't, harm was committed, and Lan Xichen didn't know how to protect him this time.

Yes they could have covered it up and let Jin Guangshan take the fall with the Jiangs none the wiser... but.. he remembered how upset Jiang Wanyin had been. He couldn't in good conscience let the boy go on thinking someone tried to have their way with him. It wouldn't change what happened but if the framing of it in a different light might ease his heart, even a little, then Lan Xichen couldn't withhold the information.

And, it really was Lan Wangji in the wrong here. If his brother ever remembered the incident he would feel horrible that he let someone else take the blame for his own deeds. So for Lan Wangji's sake as well, admitting to it was the right choice.