Author's Note: This story was written as part of the tdbk 2019 Reverse Big Bang challenge. It is a Phantom of the Opera AU, but familiarity with PotO is not necessary to enjoy the story.

Please find my partner's work, which inspired this story, on insta: stannumart (unfortunately I can't link on FFN)

Bakugou had a problem.

Well, to say he had a problem was a severe understatement. He had a bunch of them. But the strangest, and at the moment most pressing, was the man that spoke to him sometimes from behind his mirror.

"I am the Angel of Music," the man said.

"Does the angel of music have a fucking name? "

A pause. "It is not for you to know at this time."

They'd done this particular routine two times already. The mirror-man had introduced himself as some sort of secret admirer, had given Bakugou a handful of compliments, and had twice offered his services as singing coach. Twice Bakugou had given a firm "fuck no", and the voice had gone quiet after each rejection.

So Bakugou had a pretty good guess what the voice wanted now, their third time speaking. "I already told you no!" Bakugou said, before his unwanted guest even had a chance to ask the question. "I don't want any lessons. Stop asking me."

"You could be truly great," the voice said. "You could be a star."

The man's voice was monotone, barely loud enough to be heard. Bakugou wondered what sort of a person the voice belonged to, if the speaker was old or young, large or small. It was honestly impossible to tell. "You always say that," Bakugou said. "You need a new argument to convince me."

"I truly believe in your talents."

"Okay. That's nice, I guess." Unsure where to look, but unnerved by the idea that the man could see him through his mirror, Bakugou looked away. "If you have nothing new to say, go away."

"I do have something new to say. I have an offer for you."

Bakugou rolled his eyes.

"Would you like to hear my offer?"

"I know you won't go away until you tell me, so go for it, I guess."

"Alright. My offer is: if you let me give you singing lessons, I can guarantee you will be getting leading roles within the year."

Bakugou paused. When he realized that was the offer in its entirety, he threw his head back and laughed. "Now I know you're out of your mind. Do you understand that I've barely been here six months? There's about a dozen men in line for those roles ahead of me. Not to mention Enji's mostly the reason people even come to see the opera in the first place. Why would I ever get a leading role when he's here?"

"Enji will be taken care of," the voice said, steely-cold and very serious. "Do not worry about the 'how'. If you follow my instructions-"

"You never said anything about following instructions. You're modifying your agreement."

A beat. "Perhaps I wasn't done laying out the terms of the offer."

"Bullshit! I even waited to make sure you were!"

"I wasn't," the voice insisted. "Here's the full offer: if you let me give you singing lessons, and also do as I say, I'll guarantee you a leading role within a year."

"What does it mean to do as you say? What kind of commands are you going to be giving me? That's way, way too vague for anyone to agree to."

Bakugou heard the voice sigh. "I suppose you have a point. Let me reconsider this. Farewell."

"Uh, is that it? Are you just going now?" No answer. "Hello?"

But it seemed the voice's owner had well and truly disappeared. Bakugou stared blankly at his own reflection, puzzled and annoyed in equal measure.

"You did a very good job in rehearsal," the mirror-man said, as flat as ever.

A jolt going through Bakugou's entire body. It was the next day, and he'd been foolish enough to think he'd get a little more than twenty-four hours' peace. "Jesus Christ," he said, "could you warn me next time? Or maybe don't come back at all."

"I love watching you in rehearsals," the voice said, apparently unheeding. "But it makes me sad to see you playing such a small role. You don't even have any solos."

"Okay," Bakugou said, grimacing. "That's - that's - I don't know what to say. Thanks?"

"You're charming, Bakugou." The flatness of the man's voice made everything he said sound sarcastic, but it was impossible to tell whether it actually was. Bakugou didn't like that at all; he was never quite sure if he was being praised or mocked. "I've thought over the terms of my agreement. May I tell you now?"

"Go ahead, I guess," Bakugou said, with a deep, weary sigh.

"Alright. My agreement is this: if you let me give you singing lessons and memorize all of Enji's parts, I can guarantee you will get a leading role within the year."

Bakugou crossed his arms, frowning at the mirror. "Uh-huh. So how's this going to work, exactly? Are you going to kill Enji and then I'll be the only one who can step in to take his place?"

There was a pause. "Not kill," the voice said, sounding very small.

"I'm pretty sure he has an understudy. In fact I know he does - is something going to happen to him too?"

"I laid out the terms," the voice said. "It is your decision to accept or reject my offer."

"If I reject it, are you going to leave me alone?"

Silence.

"Fucking hell," Bakugou said, walking over to the mirror. It looked like it was connected firmly to the wall, but obviously there was something behind it, right? He ran his fingers along the edge of it, looking for a seam. When he found none, he pulled. Still nothing.

"Do you accept my offer?" the voice said, as flat as ever.

"How do you get behind my mirror?"

"There are a lot of tunnels under the opera house," the voice said, almost casually. "It's a very old building, you know. There are hidden passageways all over, and I know them all."

The mirror-man's lack of urgency made Bakugou think it was probably futile trying to get into the mirror this way. He stepped back, his hands dropping to his sides. "But why my mirror? Whoever built this tunnel was a pervert."

"I don't know why it connects to a mirror," the voice said. "I didn't design it. It's much older than I am."

"So there are a lot of tunnels like this in the building?"

"Yes, many."

"Do you hang around other people's dressing rooms, too?"

"Occasionally, but I visit yours the most." The man sounded almost happy, the first emotion he'd displayed openly so far. It gave Bakugou the creeps. "I don't like anyone as much as I like you."

"We've talked, what, four times?"

"I've been watching you for much longer," he said, and, oh, Bakugou did not like that one bit.

"What the fuck is your problem? "

"It took me a long time to work up the courage to talk to you. You're quite an intimidating person, you know."

"Not intimidating enough to stop you from spying on me, you little creep!" Bakugou knew people outside his dressing room could probably hear him screaming, but he was too angry to care. "If I ever get my hands on you-"

Then he was struck with an idea. He glanced around the room, his eyes settling on a large lamp that stood in the corner. He picked it up, holding it like a weapon, and prepared to swing. If there was no other way to get into the tunnel, he'd smash his way in and wring this guy's neck.

"Stop!" the voice said. Bakugou felt a thrill of satisfaction; the man was afraid.

"Give me one good reason not to smash this mirror and then your head."

"They'll make you cover the cost of the mirror. And you'll probably get fired."

"They better not make me pay for it. I don't think they will, not when I show everyone that some weirdo's been spying on me. They'll probablythank me, for revealing that tunnel."

"Everyone knows about the tunnels," the voice said. "They won't be surprised, I guarantee it."

After a long, long moment of thinking it over, Bakugou sighed and set the lamp heavily back down. He felt frustrated almost to the point of tears. He knew the voice was probably right, that he'd have to pay for the mirror out of pocket - and a full-length mirror like that was far, far more than he could afford. Particularly if the voice was also right about him losing his job.

"Bakugou," the voice said, "please don't be frightened of me."

"I'm not frightened! " he yelled. "I'm pissed the fuck off!"

"Don't be mad, either. What will make you stop being angry at me? I don't want you to be angry at me. I don't want to see you upset."

"You need to stop spying on me."

There was a long pause - Bakugou wondered for a moment if the mirror-man had taken off entirely - but finally the voice spoke again. "I will always announce when I am here. I will never come without notifying you. I will never watch you without your knowledge again."

For what felt like the trillionth time that day, Bakugou sighed. "You won't just promise not to come back?"

"I can't do that," the voice said, now back to its default flat tone. "You're very precious to me."

The whole situation was way too weird for Bakugou. He could only laugh, so he did. He laughed until there were tears at the corners of his eyes, until he couldn't catch his breath. "Why did I get stuck with the stalker?" he said, half-delirious. "Why did it have to be me?"

The mirror-man said nothing. Bakugou calmed down after a minute, wiping his eyes. "Fine. Fine. That's fine. I guess for now you can come and watch me if you need to watch me, or whatever, as long as you tell me when you're here."

"Thank you, Bakugou. ...Have you given my offer any consideration?"

"Can you fucking leave?"

"Very well. Have a good evening. Please give it some thought."

Bakugou counted sixty seconds, then said, "Hello?"

There was no response. Finally, finally, he was alone at last.

Bakugou brought a sheet from his room and draped it over the mirror. He did not trust the mirror-man to keep his word. The type of person that would spy through a mirror to begin with was probably not the type who'd stop when you asked him. Bakugou didn't want to think too hard about that creep watching him in secret before they'd even spoken - who knew how long that had gone on.

At rehearsal the next day, Bakugou decided to tell Kirishima about the mirror-man. Kirishima was a fellow opera singer, a boy about his age who'd started shortly after Bakugou; he was the closest thing to a friend Bakugou had. And he was, as far as Bakugou could tell, pretty open-minded. This was important; Bakugou needed to confide in someone who wouldn't immediately just laugh his concerns away.

But it was difficult to bring up. It took him half the rehearsal just to figure out the best way to phrase it. "Kirishima, I have something to tell you," Bakugou began.

"Yeah? What's up?"

"Have you heard about there being tunnels under the opera house?"

"Tunnels?" Kirishima frowned. "I haven't heard anything like that, but it's such a huge, old building, I guess it makes sense. That's kind of cool!"

"No," Bakugou said, "it's not cool. I think there's a tunnel behind the mirror in my dressing room."

"Where does it lead?"

"I said I think there is. I don't know. I haven't gotten in. I don't know how without breaking the mirror."

"Then why do you think-"

"Because someone's back there," Bakugou said. "Talking to me. A man." He took a deep breath. "He talks to me through the mirror, and he says he gets around the opera house using secret tunnels."

"Who is it?"

"I don't know."

"Well, what's he look like?"

"I don't know!" Bakugou said, exasperated. He was glad Kirishima wasn't reacting with skepticism, but found himself wishing he'd catch on just a little faster. "I haven't seen him! I just hear his voice. But he can see me through the mirror."

"Oh, dude, that's messed up," Kirishima said, and Bakugou felt a surge of gratefulness - at least until Kirishima added, "But how do you know it's a man? I've heard people talk about a ghost that lives in the opera house. Maybe there isn't a tunnel at all, maybe a ghost is haunting your room!"

"He said he uses the tunnels," Bakugou said. "He told me! He never said he was a ghost. I think he'd mention it, if he were."

"But there is a ghost, right? People keep talking about that. Maybe the ghost uses the tunnels?"

"He's not a ghost!"

"But how do you know, man?" Kirishima said. "You haven't even seen him!"

Bakugou felt a headache forming at his temples. "Whatever he is, I don't appreciate him watching me in my dressing room, but he won't leave. I don't know how to get him to leave."

"If it's a ghost, you could try an exorcism. Or maybe trying to get him to go to the other side. See if there's something he's left unfulfilled in this life. If it's a man…" Kirishima looked thoughtful. "Maybe the same thing? Ask him what he wants. Why's he bugging you in particular?"

Bakugou hated to admit it, but maybe the point Kirishima was making wasn't half bad. If he could find out what the mirror-man's eventual goal was, he could help it happen more quickly, so the creep could move on to the next victim. "I don't know why he's bugging me, but he keeps saying I have 'potential' and that he could make me a 'star'... he wants to give me singing lessons really bad."

"That's…" Kirishima wrinkled his nose. "Kinda weird."

"Fucking tell me about it!"

"Do you think he's a good singer? Like, could he give you lessons?"

"Does that matter? I'd rather not get lessons from my mirror, thanks!"

"I mean, I think it matters," Kirishima said. "If he's a good teacher, I'd probably take him up on it, you know? It's not like you and I are getting any private lessons as it is - they probably wouldn't even notice if we skipped rehearsal. Getting free lessons sounds like a dream."

"Free lessons from a creep who hides in the walls?"

"Free lessons are free lessons."

Bakugou didn't even mention the mirror-man's guarantee that he'd get a leading role. It was a pipe dream too strange to even bother bringing up - not to mention Kirishima, gullible as he was, would probably believe it. "I want to bring you to my dressing room so you can hear him, too," Bakugou said. "Then you can tell me if you think it's a ghost or a man."

"Cool! Yeah, sure!" Kirishima shivered. "But that's kind of freaky. I've never talked to a ghost before. What would I say?"

"Just talk to him like anyone else, I guess," Bakugou said. "That's how I do it." He isn't a ghost, he added in his head, but didn't say aloud - he knew it was pointless.

When they got back to the dressing room after rehearsal, it was obvious to Bakugou that someone else had been there in the interim. The sheet he'd hung over his mirror had been taken off, folded neatly and set on a chair. Bakugou stopped so suddenly in the doorway that Kirishima ran into him.

"I hung that sheet over the mirror," Bakugou said, his heart racing. "I hung it up last night, it was still there before rehearsal and now it's gone. My room was locked. It had to be him."

"The ghost!"

"It's - he's not a ghost!" Bakugou strode over to the mirror, staring into his own wild-eyed reflection. "Look, I know you're there, you fucker! Say something! Tell Kirishima you're not a ghost!"

It was silent. Of course it was, Bakugou thought. Of course, the one time he didn't want the mirror-man to be quiet was the one time he did. Bakugou was sorely tempted for the second time in as many days to smash his mirror clean through.

"It's okay," Kirishima said, patting his back. "I believe you, dude. He's probably just not here right now."

"Or he wants to make me look like an idiot!"

"If you're there," Kirishima said loudly, "if you can hear me, please know I mean you no harm. I come here out of curiosity alone. Please reveal yourself to me."

"He's not gonna," Bakugou said. "He's not gonna. I just know it."

They held their breath, waiting, but it was silent.

"Guess he's just feeling shy," Kirishima said. "Well, I'm gonna head back to my own dressing room, I'm beat. We can try again another day."

Bakugou waited until Kirishima had left the room before erupting. "Fuck you!" he said, slamming the side of his fist against the mirror - not hard enough to break it, but hard enough to make a satisfying thunk. "You just want to make me look like an idiot, don't you? Well, fuck you and fuck your lessons! I never want to hear your voice again!"

Silence.

In fact, the silence was so absolute, and lasted for so long, that Bakugou began to think maybe the mirror-man really wasn't there this time. Bakugou did not get a response before he left, and was deeply grateful that there were no mirrors in his bedroom. He shared his sleeping quarters with a handful of other young opera singers, and maybe the mirror-man could sneak behind a wall and listen, but that was the worst he could do there. (Or so, at least, Bakugou hoped.)

The mirror-man's conspicuous absence put Bakugou in a bad mood for the rest of the day and the entirety of the following morning. He very nearly skipped rehearsal, Kirishima's words about their presence not being missed ringing in his ears. But if he did skip, he wasn't sure where he'd be able to hide out besides his dressing room, and spending any extra time there certainly wasn't a welcome prospect.

After rehearsal, not long after Bakugou entered his dressing room and shut the door behind him, he heard a timid "Hello".

"Was wondering when you would come back, you coward," Bakugou hissed, spinning to face the mirror. "Were you laughing at me yesterday? You made me look like an idiot in front of Kirishima."

"I wasn't ready to reveal myself to your friend," the voice said, sounding almost whiny. "It took me long enough to work up the courage to speak toyou. I'm not ready to talk to a second person yet." The longer they spoke, the more Bakugou could pick up fluctuations in his mood and tone. The mirror-man's voice was not nearly as monotone as it had seemed at first. Bakugou wasn't sure he liked the idea of getting to know him that well.

"You could've at least said 'hi' or something - he probably thinks I'm crazy now. And," Bakugou added, remembering, "you came in here, didn't you? You actually came into my room. Have you done that before?"

"I had to move that sheet," the voice said. "With it there, I couldn't see you."

"Yeah, that's kind of the point!"

"I like seeing you, though."

"This is my dressing room!" Bakugou shouted. "What don't you get about that? I don't want you to watch me change!"

There was a knock on his door.

Bakugou froze for a moment, startled, before turning to answer it. In the doorway stood Aizawa, one of the directors, looking as tired and worn-down as ever. "Bakugou," he said, sighing, "we've had noise complaints." He glanced around the obviously-empty room. "Why are you shouting?"

Bakugou swallowed, his mouth suddenly dry. "Just practicing lines."

Aizawa gave him a long, searching look; he must have known Bakugou had no lines, but didn't ask any more questions. "Please keep it down in the future," was all he said as he stepped away and headed out into the hallway. When he was out of sight, Bakugou shut the door and breathed a sigh of relief.

"Why did you cover for me?" the mirror-man asked. "Why didn't you tell him you were talking to me?"

"What would I have said?" Bakugou was mindful of his volume now - he knew Aizawa could be terrifying when angry, and he didn't want to give him a reason to come back. "I know you would've stayed quiet again and made me look even crazier than yesterday. 'Hm, yes, Aizawa, I'm yelling at the asshole who lives in my mirror and really, really wants to give me singing lessons for some reason.'"

"Right! I almost forgot. Have you made a decision about my proposal?"

"You know," Bakugou said, "I want to know what's in it for you."

"What?"

"What exactly are you gaining from this? Why do you care so much about making me a star?"

The mirror-man was quiet a long time. Bakugou counted to fifteen in his head. When he finally spoke, he sounded almost solemn. "I do see a great potential in you. No other amateurs have your level of raw talent, and I believe you could be a great star."

"I will be."

"Yes, but you will be more quickly if you accept my assistance." The mirror-man paused. "Another reason... I hate Enji. I don't think he deserves to be the lead, and I want him to lose his starring roles. If it's to you, all the better."

Bakugou hadn't really known what the voice would say, but he certainly hadn't expected that. "Why?"

"That is irrelevant. I have my reasons, which don't affect you at this moment. Does that answer your question?"

"It answers that one question, I guess," Bakugou said, "but I have about a billion more."

"I don't mind. Go ahead and ask them. I enjoy talking to you like this."

Bakugou realized he hadn't changed out of his costume after the rehearsal. The sweat had already dried on his skin, and, to judge from the pervading silence from outside the room, all of the other performers had already left their dressing rooms for dinner. "Look," Bakugou said, "I want to ask you those questions, but for now I need you to leave."

"Why?"

"I want to change, so I can go to dinner."

He heard what might have been a noise of frustration from the other side of the mirror. "We've barely talked at all today."

"I've been at rehearsal all day," Bakugou said. "I'm tired and really fucking hungry, and if I don't hurry, all the food is going to be gone. Then I'll bereally pissed."

"Okay, okay." A pause. "But after dinner, could you maybe... come back?"

Bakugou felt torn. A large part of his brain - the logical part, obviously - told him not to spend any more time with the mirror-man than he absolutely had to.

Yet there was another part of him that wanted to preen at the man's flattering words, that appreciated being the sole focus. Kirishima had been right when he said this kind of one-on-one attention was rare; Bakugou could think of no other way to receive free singing lessons. Even if he didn't get a leading role, that kind of personal direction, if the mirror-man was the real deal, could be a valuable asset.

So, although he was kicking himself for ignoring all of the blazing red flags, Bakugou said, "Yeah, okay. After I eat I'll come back. But for now, look away. I don't want you to watching-"

"I'll be waiting!" the voice said, sounding distant - as if the speaker was already walking (or running) away.

Bakugou paused. "Hello?"

No answer.

"What the fuck," he said, and started changing out of his costume at last.