Chiluc fic idea that I'll probably never write but maybe someone else will!
This is a Crepus lives au. After the drake attack, Crepus was in critical condition and expected to not make it through. The Kaeya and Diluc fight still happens and once Diluc is back inside, he sees a knight approaching and assuming it's for a death notification, just runs away to not have to deal with it. They were coming to inform that Crepus had woken up.
During his time in Snezhnaya, Childe is sent to deal with him most of the time. They end up teaming up together because Diluc gets to Snezhnaya, sees the things the people are going through, from the Fatui and the Abyss and the Adventurer Guild puzzles, and starts helping where he can. He is also destroying Fatui bases and tormenting them at the same time, he's good at multitasking.
Eventually, after the Harbingers (Dottore) get really pissed and 7 of them set a trap to kill him that he's barely able to get out of, Diluc decides that maybe he should start thinking about leaving Snezhnaya for a bit. On his way out, he runs across Childe with a squad on horseback and decides "I could do with a horse" and attacks them, taking Childe's horse in the process.
She's a beautiful draft horse who is so friendly and is made of more stubborn than horse.
He gets back to Mondstadt and finds out that Crepus is still alive and is forced to have a conversation with Kaeya about what happened.
Some years later, after the Fontaine quest, Aether invites Childe to Mondstadt when he starts going stir crazy in Snezhnaya. Kaeya notices them and decides to invite himself on their day out because Aether why would you bring a Harbinger into town without informing anyone!!
Eventually, they end up at Dawn Winery and Kaeya is crossing his fingers that Diluc isn't there. He is of course, and since no one wants a fight to break out, Aether just blurts out the first thing he thinks of, which is that Childe is a Snezhnayan nobleman who's traveling. Childe isn't paying attention and has walked over to the pasture fence because he noticed a horse and started thinking "hmm, you look really similar to my horse that was stolen by the delusion thief".
He turns at the sound of his name, and lo and behold, comes face to face with said delusion thief. They stare at each other for a minute, before Diluc reaches his hand out and introduces himself. They chat for a few minutes until Kaeya drags them away to continue the tour (and get him away from Diluc)
Later that night Diluc and Childe run into each other. After a fight that either of them are taking seriously, Childe asks why he didn't say anything before? And Diluc tells him that he'd had a really bad day, didn't appreciate people he considers friends lying to his face, and really wanted to see Kaeya panic while they talked.
They start a competition with each other. Diluc loses if he reveals his connection to the Fatui or that he knows who Childe actually is. Childe loses if he ever slips up in front of Diluc in a way that would reveal his connection to the Fatui. It's a bet for bragging rights and the horse if Childe wins.
For the next few weeks they start spending more time together, trying to make the other slip up and win, going out horseback riding and showing Childe what Mondstadt really has to offer. They have a camping trip with most of the kids, and their guardians, and Childe tells about a Snezhnayan folk tale of the "Red Death" a ghost that haunts the woods with it's black chains and bird cries.
It's actually kinda nice for both of them, Diluc gets to practice his Snezhnayan for the first time in a while, and Childe doesn't have to soften himself in any way.
For Kaeya, Aether, and Paimon, it was sorta funny at first. They think that Diluc is just playing good host to who he thinks is a nobleman. Then the two of them start going on what is essentially dates, and it's a lot less funny. Kaeya goes to Jean about how much he fucked up because he hasn't seen Diluc this happy in years and it's because he's going on dates with a Harbinger who he doesn't even know is a Harbinger!
Jean drags all of them to Varka, who gets Crepus involved (he's really upset at Kaeya, but understands why he did it) they decided that they need to tell Diluc, and start trying to figure out how to go about that in a way that doesn't end with a fight.
The night they plan to do it is on family dinner night. This plan immediately goes off the rails when Aether bursts through the door halfway through, carrying a bleeding Childe.
Diluc is the first one there, asking what happened. Aether explains that they were in wolvendom to challenge Andrius, which was a hard won fight, but on the way out, Aether hadn't been paying attention and they were attacked by rifthounds. Childe took the brunt of the attack.
Diluc calls for someone to go get a healer while reaching and removing Childe's delusion from him. It's still sparking, and if anyone that isn't used to delusions touch him it could hurt them.
Jean was at dinner, so between her, Diluc, and Kaeya, they're able to stabilize him until Barbara gets there and heals him enough that he won't die.
He's brought to a guest room and Diluc stays with him the whole time. Some days later, Childe still weak and Diluc still by his side, they're finally able to drag Diluc out to talk with them.
They're all standing around the table, Crepus sitting at one end, Diluc standing at the other. Jean and Kaeya on one side, Aether and Albedo on the other. Varka guarding the door to the hallway leading to Childe's room, in case Diluc reacts worse then they think he will.
Together they all tell him. Tell him that Childe is a Harbinger, that he's a dangerous criminal. (That they've known, they've all known since the minute Childe got to Mondstadt and all decided to keep it from him because they were worried about how he'd react, like he was some dog they didn't want to bite the wrong hand. He knew the whole time, but they didn't know that)
After they finish it's just silence, they all wait for a few seconds for Diluc to say something and he doesn't, just keeps staring at them and blinking. When suddenly a voice from behind Diluc speaks. It's Childe, at the doorway of the hall, covered in bandages and leaning on the wall for support. "Well, this is awkward."
Diluc slowly turns and stares at him, everyone inching forward in case they need to jump in and restrain Diluc, when Diluc speaks. "You lose."
Immediately Childe is up in arms, ranting about how "the deal was for if i reveled it! Not if someone else reveled me!" Eventually they agree to a draw, to the confusion of everyone around them.