grow as we go

21 Dec 2025

Ali’s (very late) SangCheng Week 2025 Fics!
All either standalone AU oneshots, or a side-story to one of my existing AUs.
Prompts & specific tags detailed in each chapter.

Teen (13+)
Chapters: 7
Complete
Words: 37,366

grow as we go

Chapter 2
murder & mystery

Summary:

Jiang Cheng is stoked to finally get a murder case to investigate again. Until the most annoying person he knows turns up at the murder scene.
Or: A cute lil Murdle AU feat. Dynamic Duo Detective Jiang Cheng and Inspector Nie Huaisang

Prompt: “What lies in the dark” / Detective AU
Tags:
fluff, humor, annoyances to lovers (?), opposites attract, didn’t know they were dating
Content/Trigger Warning: mentions of death/murder

Chapter Notes:

DO YOU GUYS KNOW WHAT MURDLE IS?

MURDLE IS MY FAVORITE THING

(it is basically a puzzle book series with neat little puzzles and it has case-of-the-week vibes but there is an overarching plot and super fun characters AND AN UNEXPECTED BUT SUPER ADORABLE BL SUBPLOT!!! i just love it so i put sangcheng in it ok!!!)


murder & mystery

(a murdle au)

.

Jiang Cheng is ready for murder.

To clarify – he is ready to investigate a murder. Finally, something interesting. His latest cases have been very straightforward, boring ones – thieves that were too obvious (it was the assistant), property damages too easily figured out (seriously, it all should have been an email) and scams he very quickly saw through (that business was a front for money laundering, duh).

So this murder is good. Wait. Murder is bad. But a murder case falling into Jiang Cheng’s radar, with a mystery attached to it, that is… good. Good exercise. For his brain. Yeah. That’s what Jiang Cheng meant.

So he drives to the crime scene at the local university, equipped with his badge and his trusty pen and notepad. A senior student has been murdered. Fellow students and faculty are left in shock. It is a high profile case, the student being from a distinguished family, so the university proper has been kept under close surveillance, only authorized personnel allowed to pass through the gates, and interrogations to be done in the campus proper as much as possible.

He arrives at the crime scene, accepts the tablet handed to him with the photos of the victim and possible evidence taken when the authorities first arrived. He listens to the officer who gives him the rundown of everything they have so far.

As he pokes and prods around the area and takes in the details himself, the officer tells him that they have witnesses and possible suspects gathered, ready for questioning.

Jiang Cheng finishes jotting down key details and questions on his notepad, then tells the officer to take him there.

He follows the officer to what looks like an empty office in the university’s main building.

There, he sees one person that he really doesn’t want to deal with right now.

“Oh! Is that Detective Jiang I see? Ah – this case is practically solved then!” says a lovely, cheerful voice that has in more than one occasion given Jiang Cheng a nightmare.

Now Jiang Cheng is ready to do a murder.

Okay, murder might be too much. But it really is his first reaction upon seeing the man who waves at him with an expensive hand fan, from where he is talking to a number of very important-looking people.

Why. Why is Nie Huaisang here? Jiang Cheng laments, but he steels himself and stays professional as he approaches.

“Good day, Detective Jiang!” Nie Huaisang says with a bright smile, like there hadn’t been a murder in the vicinity just mere hours ago.

“Inspector Nie.” Jiang Cheng replies, as cordial as he can manage. “I didn’t know you’d be here.”

“Me neither! Then again, I never know where I’ll be for the day, anyway.” the other man says with a laugh.

“So what are you doing here? Please tell me you’re not a suspect.”

“Ah, we’re funny today?” Nie Huaisang grins. “Don’t worry, it’s just the usual. Inspecting. The family wanted more hands than what’s on the ship to be on deck. So our agency got a call to assist.” Nie Huaisang says simply. “Are you taking point on this? What a pleasure. I love assisting you!”

Jiang Cheng takes a deep breath that is almost a miserable sigh. “Great. I… am grateful for the assistance.”

“I also just got here, y’know? And the nice officers told me these here are the last people who were seen with our victim. We haven’t talked that much, but you probably have better questions than mine. Please, ask away!”

Okay, Jiang Cheng thinks. This is going fine so far. Nie Huaisang is… fine. Jiang Cheng has worked with him before. He can work with him again. He has no choice, anyway. Nie Huaisang’s home agency is quite well-known and respected, and Nie Huaisang’s brother is Jiang Cheng’s boss. Jiang Cheng doesn’t want to upset Captain Nie. Nope.

(Though Captain Nie himself always complains about his own brother. But that’s another matter altogether.)

Sure, Jiang Cheng may want to go kick something later. But that’s later. It may not be so bad right now.

The officer introduces him to a chancellor, a dean, and the janitor. All of them were witnessed with the victim hours prior. None of them had denied that fact, and were willing to give their full cooperation.

For efficiency, Jiang Cheng requests to interrogate them one by one. He doesn’t tell Nie Huaisang what to do, and it looks like he doesn’t have to worry about that for now. The man seems to have settled sitting cross-legged on the professor’s table, reading the university newspaper.

Of course he’s on the Horoscopes section.

Jiang Cheng interrogates the janitor first. He asks the routine questions – the where-were-you’s and what-were-you-doing’s – followed by the specific ones – the classic how-do-you-know-the-victim and what-did-you-two-talk-about.

He jots all that down on his notepad as well, drafting down a grid table with well-practiced ease, filling it in with information, marking crosses and checks…

“What-… What are you-… I swear, I really didn’t see the kid after that-” The janitor, leans in, looking curious and worried, as people often got when someone starts writing things down after they’ve spoken. He only gets a glimpse of Jiang Cheng’s notes before the notepad is closed and held away from him. “Are you-… Hey, man- I mean, sir, are you playing Clue?”

Jiang Cheng frowns. “How I take down notes is none of your concern, Mr. Wan.”

“The Detective is working, Mr. Wan.” Nie Huaisang says from his perch on the table. “He is the best in his department, did you know? He is so good and he solves stuff so easy like it’s just Clue!”

Jiang Cheng turns his head to send the other a look, but it looks like Nie Huaisang is still busy with his reading-

“Hey, so, what is your zodiac sign? Mr. Wan, I mean- I already know our dashing detective’s a Scorpio.”

Jiang Cheng takes a deep breath. It’s starting.

He watches as the janitor, Mr. Wan, looks towards Inspector Nie in bewilderment. “Uh-… S-Sagittarius? How is this related-”

“Hm, oh! Here, today’s fortune: ’You may face unexpected challenges that test your resilience. Stay calm and positive.’ Well. I think you are doing a good job staying calm, Mr. Wan.”

Mr. Wan looks more confused. He does try to muster up a smile, though it looks more like a grimace. “A-Ah… I don’t… really believe in that, but that… sounds nice? Thank you…?”

Jiang Cheng takes pity at the very confused man. “I think that’s all the questions we have for now, Mr. Wan. Thank you for your cooperation, you may go. We’ll contact you if we need more information.”

Mr. Wan thanks him as well, and goes. As they wait for the next witness to come in, Nie Huaisang pipes up.

“I don’t think it’s him, Detective Jiang…”

Jiang Cheng walks towards him and crosses his arms across his chest. “And why do you think that is, Inspector Nie?”

“He’s just so nice…” Nie Huaisang shrugs. “Don’t you think he’s been quite nice?”

“That’s not an alibi.” Jiang Cheng says, though he couldn’t help but grumble, “He has a solid one, though.”

“See? Oh, would you like me to read your daily fortune too?” Nie Huaisang smiles as he goes back to the paper.

“No, thank you.”

“Hm… Too bad.”

The Dean arrives next. Before Jiang Cheng could ask a question, Nie Huaisang raises his hand to wave at their potential suspect. “Hi, Professor Dean, m’a’am? Do you want to know your fortune for today?”

The Dean blinks, but spares a well-practiced pleasant smile for the man. “Thank you, Inspector, but there’s no need. I already checked mine. I even wore my lucky color today… Didn’t seem to work, though… Such a tragedy, our poor young Mr. Li…”

“It is.” Jiang Cheng interjects, narrowing his eyes at Nie Huaisang. Nie Huaisang just smiles innocently at him before waving him off, towards the Dean who has taken a seat, ready to answer questions.

Jiang Cheng goes through the same questions with the Dean, plus some specifics and clarifications to iron out some details.

Then they send in The Chancellor, who was also very cooperative and patient as he answers their questions. A couple more people also get brought in, those who saw the potential suspects with the victim, and fellow students who belong to the deceased young man’s circle of friends and acquaintances.

Jiang Cheng jots all the information down on his trusty notepad, making steady progress in his investigation.

Now and then, Nie Huaisang interjects with one of his absurd questions. He asks the Chancellor about his zodiac sign as like he did the others. He mentions some kind of numerology thing when a student came in wearing a jersey with a number. He says something about Mercury. At one point, he somehow manages to get Jiang Cheng to sit down with him and listen to one of the professors telling some sort of popular campus ghost story.

See, this is why Jiang Cheng doesn’t like working with Nie Huaisang.

Nie Huaisang asks so many questions. Jiang Cheng is usually okay with questions. The thing is, Nie Huaisang asks totally unrelated questions – sometimes distracting the person they’re interrogating – sometimes even distracting Jiang Cheng. Because it’s usually about things that Jiang Cheng knows doesn’t help him with their investigation at all. Things that Jiang Cheng doesn’t exactly subscribe to.

Jiang Cheng is a creature of logic. He figures things out by putting the When-Where-How-What’s down on a neat grid and then using the tried-and-tested process of elimination and substitution to arrive at a conclusion. Meanwhile, Nie Huaisang firmly believes in the power of the stars to influence one’s destiny, lucky numbers, magical stones, ghosts, superstitions, and all that stuff. Sometimes he even moves stuff around unprompted, just to “fix the energy” of the place. And he really shouldn’t be moving stuff around in a crime scene.

What really irks Jiang Cheng the most though, is that it does work for Nie Huaisang. He doesn’t know how the hell it happens. It just does.

One time, he managed to identify a suspect before Jiang Cheng did, and only said, “I dunno, Jiang-xiong, he just gave me heebie-jeebies…”

It is. Extremely. Annoying. Jiang Cheng doesn’t understand it. Jiang Cheng hates it when he can’t understand things. And when someone moves stuff around in a crime scene.

(Seriously, that shouldn’t be allowed. How does he even keep getting away with it?)

Now, Jiang Cheng sits on the table beside his… associate… who passes the school paper to him, clearly done reading it. Halfway through the interrogations, he claimed that the advice column was very entertaining.

“So… your daily fortune tell you who did it?” Jiang Cheng says, as he takes the paper.

“I have a hunch…” Nie Huaisang says, scooting closer to him and leaning on his shoulder.

He does this often, as well. Jiang Cheng… allows it, mostly. This way he knows exactly where Nie Huaisang is. Right beside him. Not poking around the evidence and moving important items in the crime scene, interfering with the investigation.

The only downside of this is Wei Ying starts calling Nie Huaisang his “boyfriend” (very juvenile), Captain Nie looks at him weirdly (like some mix of confusion and approval), and Jiang Cheng finds himself wanting to… well… not move (because it’s kinda nice?). But those are all manageable.

Nie Huaisang pokes his arm. “I bet your Clue thingy already gave you an answer, though.”

“It has.”

Jiang Cheng absently skims the paper – headlines, photos, some of the people they interrogated during the past hours are featured as well-

“I just want another detail that really will confirm- Huh. Look at that, there it is.”

Nie Huaisang blinks, then looks over to where Jiang Cheng points at a featured photo in one of the news articles.

“The murder weapon-… Here, he’s left-handed-”

“-and a Gemini!”

They look at each other.

“Sure. Whatever that means.” Jiang Cheng sighs. “Is he your guess too?”

“Yup!” Nie Huaisang says proudly, and doesn’t offer any explanation other than “He has bad vibes, A-Cheng.”

It’s fine. Jiang Cheng probably won’t get it. Just like when he once tried to explain his logic tables to Nie Huaisang, who absolutely did not get those either.

He simply nods, tucks the school papers under his arm and starts to walk off.

“Alright, I’ll get a warrant for the chancellor.”

.

.

.

“To another case solved! Detective Jiang makes it look so easy!”

“Hell yeah, to Detective Jiang!”

Jiang Cheng shakes his head, but does give in and clinks his bottle of beer with Nie Huaisang’s and Wei Ying’s over their table of hotpot.

He has ended up here, somehow.

Nie Huaisang apparently wasn’t done terrorizing him for the day even after they solved the case. He got into Jiang Cheng’s car just as Jiang Cheng was leaving the university, saying that he was also going to the station anyway to see his brother, ”so thank you for the ride Jiang-xiong!” He hung around Captain Nie’s office for the rest of the day. Then just as Jiang Cheng’s shift was ending, he somehow convinced Jiang Cheng that they were gonna have dinner and drinks together. He even had Jiang Cheng’s brother tag along.

Jiang Cheng is starting to think that he may be some sort of hypnotist.

That, or they’re dating.

It’s probably the hypnotist thing.

“Jiang-xiong is so cool, he looked like he was just bored earlier…” Nie Huaisang says, like he has to hype Jiang Cheng up for Jiang Cheng’s own brother. He really doesn’t have to.

Wei Ying clicks his tongue at his brother, his grin teasing. “Aw, Jiang Cheng, there was a murder and you were bored?”

Jiang Cheng rolls his eyes. “I just honestly thought it’ll be more difficult to figure out.”

“Yes, yes, you are too good at your job…” Wei Ying says, chuckling. “Move to our department, Cheng-cheng! Change of scenery? It’s not as boring as it looks.”

Jiang Cheng grimaces at the thought of doing the same work his brother does. He respects it, but he doesn’t want to do it. “No thanks, I don’t like actually poking dead bodies.”

“Right, you can’t transfer, Jiang-xiong~” Nie Huaisang whines. “You’re the only hot detective I work with… All the others are old and grumpy and they don’t believe in horoscopes! Truly discouraging… How would that motivate me to go to work?”

“I don’t believe in horoscopes either, you know.” Jiang Cheng frowns.

Nie Huaisang shrugs. “Sure, but you like me, at least.”

“I don’t really like you either.”

“This is very Scorpio of you to say.”

“I don’t know what that means.”

Nie Huaisang pouts, and looks for an ally across the table. “Wei-xiong, look at him being mean to me… I behaved today and wore gloves to handle evidence and everything!”

“Behaved- You were running off with that vase from the Dean’s office!”

“I was taking it outside because it was attracting negative spirits!”

“Jiang Cheng, don’t be mean to your boyfriend.” Wei Ying says, though he is too busy eating to really pay attention to them. “He tries to protect you from negative spirits and stuff.”

“The only negative spirit in that place is their murderer of a chancellor.” Jiang Cheng huffs. “And he’s not my-”

Nie Huaisang’s phone chimes then, and he is quick to check it and read the new message. “Oh! I gotta run now. Looks like I have a case…”

Both brothers look up from their food to watch him gathering his things and picking up his jacket.

“Like, right now, Nie-xiong?” Wei Ying asks, blinking.

Jiang Cheng, just because he’s in danger of being slapped on the face with a sleeve as Nie Huaisang flails around trying to wear his jacket, helps Nie Huaisang into it. “It’s late.”

“Yeah, the perfect time to inspect a haunted house! Well. Allegedly haunted.” Nie Huaisang says, smiling as he pats his jacket down. “Cool, right?”

“What time are you even getting home?”

“Hopefully not super late.” Nie Huaisang only shrugs as he puts his sling bag on next. “Why, will you pick me up and drive me home again?”

Jiang Cheng also helps him with his bag, because the strap got stuck in his jacket collar. He thinks about the question. It is not his job to drive Nie Huaisang home. But… Nie Huaisang is his friend, kinda. And Jiang Cheng is willing to help a friend, if it’s within his means.

“I mean… if you really need someone to?”

“I’ll send you a message so you don’t worry.” Nie Huaisang pats his shoulder, then sends a bright smile to Wei Ying. “It’s good to hang out again, Wei-xiong!“

Wei Ying smiles back. “Good luck with your case, Nie-xiong.”

“And thanks for the treat, A-Cheng! Today was fun.”

“Yeah, don’t get got by ghosts or whatever.” Jiang Cheng nods, leaning in when Nie Huaisang tugs at his arm.

“Roger that, Detective Jiang.” Nie Huaisang laughs, and kisses his cheek.

Then he’s off, only stopping once by the restaurant tip box to drop a bill inside. He waves goodbye at them by the entrance before disappearing.

“So… what were you saying, again?” Wei Ying starts, as they go back to their dinner. “He’s not your-…?”

Jiang Cheng stares down at their hotpot.

He thinks of their interactions today-… no, the past months, of the messages between him and Nie Huaisang on his phone, of the regular dinners after shared cases that always end with a goodbye hug or kiss, of him losing his trail of thought everytime Nie Huaisang babbled on about paranormal stuff to a suspect they were investigating, of the tiny obscure good-luck trinkets that now grace his work desk plus his car dashboard, and lastly… of Captain Nie just assuming he’s coming to Great Aunt Nie’s birthday next week.

“Shit. I think he is my boyfriend.”

Wei Ying laughs. “Really? How’d you figure that out?”

Jiang Cheng picks up his drink. “Logic.”

He takes a swig of beer. Then he takes his notepad out, and jots down a reminder to ask his sister for advice on what gift to get for Great Aunt Nie.

.

.

.

fin.


Chapter Notes:

captain nmj: it’s kinda awkward that one of my officers is dating my brother but whatever
jc: phew must be awkward for that officer too haha
wwx: …who’s gonna tell him?

(Nie Huaisang Inform Your Boyfriend That He Is Your Boyfriend Challenge)


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