Mezou led them through winding, chaotic streets to a small building that was little more than a hole carved into the base of one of the giant stalactites that dotted the Depths. Hidden by several larger structures and nearly invisible from the outside, Izuku recognized it as a simple bolt-hole right away. It made sense that someone like Mezou would have a series of small, well-hidden bases that could serve as refuges or resupply points. It spoke to a practical, intelligent side of the man that might not be evident from his initial hulking appearance.

Izuku had already known he was dealing with something other than a garden-variety criminal here-the way Mezou had effortlessly dispatched an entire gang while barely breaking a sweat was proof of that-but the way he swiftly ushered his guests into the small, rough-carved room, sealed the door behind them, and sprawled himself across a plain chair with all the languid menace of an apex predator was yet another reminder that this was a vigilante in a place where there were no heroes to aspire to.

Mezou's eyes seemed to flicker in the faint, homely glow of the overhead light as he stared at Mina and Izuku, who slipped into chairs across from Mezou, separated by the small table that was about the only other piece of furniture in the bolt-hole. His inhuman jaw seemed set firmly, and the three sets of arms crossed over his chest made Izuku think, bizarrely, of an intertwined net of sturdy rope.

One of those hands dipped into a pocket in the enormous cargo shorts he wore, pulling out a nondescript brown box. Mezou opened it without even sparing the hands doing so a glance, revealing thick, crude cigars. With all the panache of a mafioso, he pulled one out, produced a lighter from a different pocket, and lit it.

As Izuku fought back a gag from the sudden, overpowering stench, Mina simply frowned. "You're still doing that shit?" she asked. "I thought your…I thought you stopped."

Izuku noted the abrupt correction, though he had no idea why Mina seemed so hesitant. Mezou rolled his eyes. Through clamped teeth, he muttered, "Why do you think I'm doing it here?"

Mina nodded, but before she could speak, Izuku coughed out, "Seriously, what's up with that stuff? I can't imagine what it's doing to your lungs."

Mina gave a snort of amusement, surprising Izuku. Mezou, though, shot Izuku a hateful glare.

"I have a regeneration quirk, you half-brained hero. I can literally just grow new lungs whenever I want. Now, do us both a favor, and shut up," he demanded. Izuku obliged, figuring it was best to avoid pissing off the only man who could help him.

Strangely, Mina came to his defense. "He may be half-brained, but he has a point," she replied. "You may be immune to cancer, but we're not. Put that shit out or I'll melt it."

Mezou glared at her, but Mina met his gaze without flinching, acid bubbling from her fingertips. Izuku couldn't quite get over how strange it was to see her face-she'd removed her cloak, mask, and even her gloves, revealing a tight-fitting black outfit reminiscent of a jumpsuit underneath. Clearly, whatever her relationship to Mezou had been, she felt comfortable enough around him to show her face. Izuku wondered why that thought made him force down a spark of jealousy.

Eventually, Mezou sighed, removing the cigar and stubbing it out before tossing it away. "I see you still haven't changed," he grumbled. "I swear, every time I went for one of those, you'd take me to task."

Mina grinned, eyes sparkling playfully. "It wasn't always me," she pointed out, seemingly enjoying the back and forth. "The only person who hated those things more than I did was-well, was your girlfriend."

In the middle of her sentence, Mina glanced at Izuku for a second, then hesitated, tripping over what he could only assume was a name she didn't want him to know. He tried not to take it personally-he could only imagine that they didn't want to risk him taking that information back to the other heroes.

Still, even as Mina winced at her accidental reveal-something that Izuku found both confusing and, oddly, relieving-Mezou couldn't help but grin, his eyes growing distant and fond. There was still that pain in them, though-it appeared every time he looked at Mina, and Izuku had no idea why.

"Oh, yeah, you wouldn't know," Mezou said, his voice wavering between gruffly hostile and oddly friendly. "She's, uh, not my girlfriend anymore."

Mina sat up straight, shock clear in her eyes. "Y-you didn't…break up, did you?" she asked quickly. The pain in her eyes was too strong to be from learning of an old friend's failed relationship.

Mezou shook his head quickly. "No, absolutely not," he quickly corrected. "We got married, actually."

Izuku blinked in surprise. He had been pretty sure Mezou was about the same age as him and Mina, mainly because of how he and Mina spoke of their past. But the man was married? That couldn't be right.

Judging by Mina's gasp, though, she seemed more gleeful than shocked, although it was tempered by a pained hitch in her voice. "You're kidding!" she said, happier than Izuku had ever seen her. "How long?"

"Almost a year, now," Mezou answered, something that might have been a smile flitting across his features. "Still don't know how the hell it happened."

Mina snorted. "She's still too good for you, Mezou," she told him, before her face fell again. "I can't believe I missed it."

And just like that, the moment shattered. Mezou's face grew grim again, aided by the way he suddenly seemed to remember that Izuku was present. Mina seemed to wilt like a dying flower, shrinking back into the hard, prickly woman Izuku was familiar with. He felt like he had just caught a glimpse of some past life, or of a different world. He didn't know how to reconcile the bitter, angry thief with the cooing best friend learning about a marriage.

Somehow, he thought that Mezou and Mina were having the same problem. The way they looked at each other was like they were trying to paste an old memory over the person who existed now. They fell so easily into something close and free, a relationship that Izuku couldn't even begin to guess at…and then froze as soon as they realized what they were doing. They were awkward and stilted as they looked at each other, and pain prickled like broken glass between them.

"What did Mina do to him?" Izuku found himself wondering.

"Alright, that's enough catching up," Mezou began, his voice low and ominous. It seemed he'd realized the same thing Izuku had. "Talk. Fast."

Mina met his eyes; Izuku decided it was wise to let her go first. Furrowing her brow in confusion, she asked, "What's with the hostility all of a sudden? I thought you said-"

Before she could finish, Mezou interrupted, "I said I'd talk to you. What you told me got you in the door. Now you have to convince me."

Izuku took a deep breath. Something about the way Mezou reclined in his chair made danger roll off of him. Maybe it was the way the tiny space only made him feel even bigger, or the way his eyes never missed any movement Izuku made, or how every muscle in his enormous body seemed to be tense, ready to move explosively at a moment's notice. Izuku could feel the mood teetering on a knife's edge.

Mina's eyes narrowed. "I'm not lying," she said harshly, her voice nearly accusing. "You know that, Mezou. I'm serious when I say I think we can figure out what happened to him."

"I believe you," Mezou replied. Izuku found himself still as confused as ever. Mina had never mentioned anything about this mysterious man. Why was she willing to bring him to the Depths if it meant she could learn their fate?

"Then are you going to help, or not?" Mina demanded. Her voice was cracked and heavy, as though she was dredging up a hundred different long-buried pains. It was the most emotional Izuku had ever heard her voice.

Mezou met her eyes, as steady and controlled as ever. "You haven't even told me what you want from me," he pointed out. "And I'm not going to fall over myself to help him."

One of Mezou's fingers jabbed accusingly at Izuku, who did his best to avoid being startled. Mina didn't even turn her head.

"You really can't let that go, can you?" she snapped.

"Do you expect me to?" Mezou retorted, suddenly leaning forward. His eyes seemed to spark with anger. "You brought a hero to the Depths, Mina. And not just any hero, you gave Atlas the grand fucking tour! Do you know how dangerous that is? How many people you've put at risk?"

Mina's eyes flared, but before she could speak, Izuku did.

"It isn't dangerous," he said calmly, holding firm under Mezou's deadly glare. "You have nothing to fear from me. Once I'm done, I won't return here or put you or those you care about in any danger. You have my word."

Beside Izuku, Mina turned to look at him, though Izuku couldn't see the look on her face. He was too busy meeting Mezou's gaze. The vigilante's eyes were burning, filled with anger that took Izuku's breath away. It was too deep, too old, too pure to be because of something Izuku had said. It was like staring into a volcano. But still, Izuku didn't flinch.

Mezou leaned forwards again. "Your word means nothing to me," he growled. "You'll break it as soon as it's convenient for you. Heroes always do."

Izuku wanted to protest, but again, he knew it would be fruitless. Heroes were hated down here for a reason, after all; the most interaction the majority of those in the Depths ever had with them was either getting arrested themselves, or watching friends or family hauled away, disappearing into prisons infamous for being dangerous for mutants. There were a lot of things wrong with the Japanese justice system, he knew-brutal treatment of suspects, railroaded trials, cruelly long sentences even for minor offenses. Being a mutant made those things ten times worse, to boot. Izuku could only imagine that resentment of heroes and police ran deep here, festering like an open sore that was never treated.

Putting aside fruitless thoughts, Izuku nodded softly, acknowledging the point. "I know you have no reason to trust me," he admitted. "But I'm after a very dangerous criminal, one who poses more threat to mutants like you than anyone else."

Mezou raised an eyebrow as he leaned back in his chair again, some of the hostility fading from his eyes, replaced with cautious interest. It seemed Izuku had guessed correctly-the man was highly protective of other mutants. Perhaps he saw himself as some sort of protector.

"Is this true?" Mezou asked, looking not at Izuku, but at Mina-it seemed his distrust still ran deep.

Mina nodded. "It is," she confirmed. "He explained it to me-and not a moment too soon. When he asked, I was about to walk out because I thought he was trying to make me an informant. I nearly attacked him, even. Sorry about that, by the way."

Mina nodded at Izuku as she finished speaking. It wasn't much of an apology, but given the circumstances, Izuku figured it was good enough. Besides, from what he understood now, he couldn't really blame Mina for reacting poorly-she clearly saw informing on other mutants for the heroes as a betrayal of the highest order, and it ran against the prideful, stubborn streak that ran right to her core. If he'd known, Izuku would have never brought it up the way he did.

But what was done was done. He nodded in return, accepting the apology wordlessly. Then, he turned back to Mezou, who was staring thoughtfully at the wall behind Mina and Izuku.

"What kind of criminal?" he demanded. His voice wasn't quite as hostile as it had been, but it wasn't friendly, either. Clearly, he hadn't decided to help them yet-but he was willing to hear them out.

Izuku took the opportunity. He began, "A serial killer named Himiko Toga. She's a former member of the League of Villains, and known to be inspired by Hero Killer Stain."

Mezou nodded. "I'm familiar with the League, and Stain disciples," he said, to Izuku's surprise. "They're a dime a dozen down here. Mostly just thugs and former gang members gathering under a fresh banner, but there's some real fanatics, too. I have to admit, I've never been surprised at how popular they are-this place hates heroes."

Filing away that information, and fighting down a long-dormant memory of a sword stabbing downwards at Tenya Iida's helpless body, Izuku continued, "A sidekick of mine working on her case managed to figure out her attack patterns for these last few years. She's been down here, attacking mutants every few months. She must have killed…dozens, at least. Probably more."

Mezou growled somewhere in the back of his throat. Exhaling loudly, he stared down at Izuku with a strange, analytical glint in his eyes.

"You're angry, aren't you?" he asked, arms crossed over his chest. "You're pissed about this Toga character running around right under your nose."

Izuku clenched his fists. Letting out a shaky breath, he admitted, "Yeah, I am. This…I didn't come down here because I'm just working a case. This is personal."

"Why?" Mezou asked harshly, startling Izuku. "You can't stand a member of the League staying free, as a big black mark on your perfect little record or something?"

Izuku bit back a sharp retort. Instead, he replied, "No. I'm angry because dozens of people are dead, thanks to my failure. I didn't realize there was a serial killer running loose, and she got away with killing people who had nobody to protect them. I need to stop her, so that nobody else suffers because of her-because I couldn't catch her before."

Mezou snorted dismissively. "Why do you care?" he asked pointedly. "You said it yourself-her victims were mutants. Some of them were probably criminals, just like Mina and I are in the eyes of your laws. You and I both know you'd rather lock criminals in jail than protect them."

Mezou's words hit hard, making Izuku wince ever so slightly. Next to him, he could feel Mina's eyes on the back of his head; it seemed that she'd had a similar question, though she hadn't asked it. Once again, Izuku got the sense of a knife balanced over a tipping point, about to fall one way or the other.

Izuku took a deep breath. "It doesn't matter," he answered. "It doesn't matter who they were or what they did. They were murdered, and I blame myself for it. One sin doesn't justify another-and if I'd been able to stop their deaths, I would have."

Mezou frowned slightly, but he didn't say a word. Silence filled the small room, as Izuku refused to bend under the gazes of two of the most powerful mutants he'd ever known.

"The way I see it," he added into the silence, "cooperating here is a win-win situation. I take down Toga, and you get a dangerous criminal out of your hair."

After an achingly long moment, Mina joked, "I'm telling you, this one is the strangest abovegrounder I've ever met. When he talks, you almost believe him!"

Mezou snorted. "Yeah," he agreed. "Almost."

Then, out of nowhere, Mezou slammed a hand down on the table, startling Izuku as the enormous man leaned in closer to him.

In a low, steady voice that rolled like thunder, Mezou said, "You seem to have some misconceptions about me, hero. So let me make something abundantly clear. I'm not the kind of pathetic hero-wannabe vigilante you're probably used to aboveground. Down here, I am vengeance. I don't do what I do because I wish I could be a hero. I do it because if nobody else will stand up to the real monsters down here, then I fucking will. The kind of people I stop are the absolute worst of the worst, the ones who never deserve to see the light of day. But that's a tiny fraction of the people you heroes shove down here. So I don't fight crime like you heroes do. I fight evil. The difference is bigger than you'd think."

For a moment, staring down a man who seemed impossibly larger-than-life, Izuku found himself recalling that bar, and the look on Mezou's face as he waded through nearly a dozen men because someone innocent was in danger. There had been rage there, yes-but there had been glee, too. There was something primal in this man, something that exulted in righteous fury, in destruction. It was like staring down a force of nature.

Izuku searched for an answer, but couldn't find one; he wasn't sure if it was because one didn't exist, because he didn't want to anger the only man who might be able to help him, or simply because some part of him, the quirkless boy who'd always wondered what he'd done to deserve the scorn he'd received, found Mezou's words hitting a little too close to home.

So instead, Izuku wondered, "What did I do to make you hate me so much?"

Mezou studied him for a long moment; his alien features made reading his expressions difficult if he wanted you to read him, and utterly impossible if he didn't. "You? Nothing," he admitted eventually. "What you stand for? The Underground you come from? More than you could ever hope to fix."

Izuku frowned."You talk about the Underground like you're not a part of it," he observed, confused.

Anger made the immense man on the other side of the table practically radiate danger, making his presence fill the room, all originating back on that roaring fire in his eyes. Mezou growled, "We aren't. There's the Underground, and then there's the Depths. One exists in the eyes of the surface, and the other one doesn't. Why would I associate with a world that offers me nothing?"

Izuku's hero heart couldn't sit idly by and take such words. He began, "The world can offer you more, if you just-"

"If I what? Give it another chance?" Mezou interrupted, his voice cracking like a whip with icy, devastating precision. "No. I've given it too many. Time after time, people like me and Mina have asked for kindness, for the dignity and respect we are owed. We've never gotten it. I will not go begging for the right to stand tall. I will not be humble for the benefit of those who call me monster. People like us have been told by the world you protect again and again that we don't deserve to be called human. Is it any wonder we no longer listen to anything you say?"

Izuku looked to his side, where Mina sat quietly, staying out of the conversation, her golden eyes staring firmly at the corrugated metal of the table. He wondered what she was thinking, if she shared Mezou's view of the world. He had heard traces of it before, in her voice; little moments of bitterness, a deep melancholy and frustration. But he saw himself in those emotions, as he saw himself in the righteous fury Mezou wore so openly, so proudly. So Izuku asserted, "You are human. You're no different than I am."

As Izuku spoke the words, he understood that he'd recognized the truth. He'd finally acknowledged the whisper he'd been hearing ever since a mask had come off to reveal the most beautiful eyes he'd ever seen. He'd never truly believed any different-long years of being discriminated against himself had always given him enough perspective to doubt the lies fed to him about mutants-but for the first time, he could spot the lie in himself, and burn it from its hiding place. It was rooted deep, but Izuku swore he'd learn to find it and rip it out, every last bit of it.

Mezou's expression didn't change. If anything, the deep blaze in his eyes only strengthened…until at last, Izuku recognized it. It was the fury of a whole people, the raw, unfiltered rage of all those who no longer saw the point of pretending to value a world which had shoved them aside. It spoke to him, to the quirkless boy he'd never quite left behind, as nothing else ever had.

Mezou's gaze pierced through Izuku as surely as a blade would have as he growled, "Am I? I've spent my whole life down here, in the dark and the damp. I have never seen the sun, or the blue sky; my whole world is the stone under my feet, the earth all around me. The only light I know is artificial. Can you say the same, abovegrounder? Do you know what it's like to have never tasted air that wasn't recycled, water that doesn't taste of stone? You are sun-kissed, windswept, rain-touched. Are you and I the same?"

Izuku shivered at the picture Mezou's words painted; he couldn't imagine a life spent like that, in the endless caves of the Depths, crawling like rats, unable to feel the heat on your skin. But, then, he supposed any Depths-dweller would have had trouble imagining his life, too. They would have been befuddled by the thought of a light too bright to stare directly into, by the idea of bodies of water too vast to see across, too salty to drink. Perhaps it wasn't nature that defined a person, but a spirit. Perhaps two human beings from worlds so different as to be nearly unimaginable to one another could still recognize each other, if they were to meet. Izuku met Mezou's eyes across the gap, and did just that.

Slowly, forming his words as he went, Izuku answered, "We are, I think. We dream the same dreams, have the same hopes. We…we love and hate the same way. For the same reasons."

Mezou didn't reply. The longest silence Izuku had ever conceived of seemed to follow, his words echoing into cold, empty air until all was still.

Only then did Mezou speak. Stroking his chin with one of his many hands, anger slipping away as if it had never existed, the immense mutant mused, "Hmm…Mina, you're right."

Mina looked up in startled surprise, clearly shocked to be jolted from her quiet solitude. "I am?" she repeated.

Mezou nodded. Jabbing a finger forwards to point at Izuku, he said, "This is the strangest abovegrounder I've ever encountered."

Izuku blinked in surprise as Mina eyed him up and down, then snorted, "Believe me, I know."

Izuku chuckled softly, at least until a thought struck him, brought on by Mezou's words. Quietly, as though scared of the answer, he asked, "Mina…have you ever seen the sun?"

Once more, there was silence. Mina looked away, refusing to make eye contact. She drew into herself, as though shrinking down to protect something precious inside her chest. Izuku cursed himself for pushing too far, for asking about things he had no right to know.

Just as he despaired of how stupid he'd been, Mina's soft, weak voice came, answering, "Yes. A long time ago."

Izuku blinked in shock. Before he could think, questions spilled out of his mouth. "How? When?" he asked, far too quickly. Far too harshly.

Mina flinched, ever so slightly, though Izuku didn't know if it was from his words or from memories he wasn't privy to. The moment shattered, and Mina said in something like her usual voice, "Forget about it. Mezou, will you help us or not?"

Drumming his fifteen right-hand fingers on the table with a sound not unlike a small marching band, Mezou replied thoughtfully, "I…think I will."

"Really?" Mina asked, evidently surprised.

"Yes," Mezou confirmed with a nod. "If nothing else, you're my friend. That should still mean something, I think."

"It should," Mina agreed, with the air of one who wished it was always true.

A moment later, Mezou added humorously, "Also, if I said no, you'd probably just go tell my wife."

"That was the plan," Mina admitted with a chuckle. "She would have made you help either way."

Izuku and Mezou's eyes met again. There was still dislike there, but it was muted, now. It seemed Mezou had decided to put up with him, at least for a little bit.

"There's a Neo-Stain stronghold here in this cavern," Mezou told him. "I've heard that people have seen a young woman with them, with blond hair and yellow eyes. Supposedly, she's been recruited recently by their leader; rumor is that she's the craziest killer in the Depths. Now, to me, that sounds like your target."

Izuku nodded, thinking of Ejiro's warning. It made too much sense that Toga would have fallen in with fellow Stain followers. Well, it wouldn't be anything he couldn't handle.

"Thank you," he said meaningfully. "I can take it from here. I won't bother either of you any longer."

Izuku went to rise, only to find Mina grabbing him by the wrist. "Oh no you don't," she told him. "I'm helping."

Surprised, Izuku stared at her, only to be met with a cocky smirk and a stubborn look in Mina's eye, as if inviting him to try and stop her. Behind her facade, though, he got the sense that Mina was deadly serious on this. For some reason, she looked as though she might fly apart at any second-but she was still going to come.

Eventually, Izuku decided that there was no point in starting a fight he wouldn't win. He sighed, "Okay."

Mina grinned. A moment later, Mezou added, "I'm coming, too."

Izuku and Mina both whirled in shock to stare at him. They were greeted by a thoroughly unimpressed-looking Mezou.

"You think I'm about to let the Number One Hero go gallivanting across my city without me there to keep an eye on him?" he asked jokingly.

Mina raised an eyebrow. "Oh, I'm sorry, do I not count?" she countered.

Rolling his eyes, Mezou answered, "Of course you do. I'm pulling double duty as your babysitter."

Izuku's eyes widened fractionally, while Mina spluttered angrily. At last, she snapped, "I do not need babysitting."

Mezou gestured at Izuku. "The last time I let you out of my sight, you brought this fucker here," he pointed out.

Mina leaned back in her chair, crossing her arms petulantly. "The last time you let me "out of your sight" was six years ago," she muttered. Izuku found himself once again wondering what kind of history Mina and Mezou actually shared.

He got a small hint a moment later, when something painful flashed in Mezou's eyes, and he said softly, "Yeah. Because you ran away."

Mina froze, and the moment snapped for a second time. For a second, nobody moved or spoke.

At last, Mezou stood, the table creaking from the force as he pushed down with several hands at once. He declared, "Well, the sooner we do this, the sooner we get the abovegrounder out of our hair."

Izuku raised an eyebrow, but decided not to speak. The wisdom of that decision was proven a moment later, when Mina sighed, "Believe me, he's annoyingly persistent. He chased me across half the damn Underground just to ask why I saved his life."

Mezou turned to regard Izuku and Mina strangely for a moment; hard, flinty eyes sparked with something Izuku couldn't quite name. At last, he shook his head in resignation, and muttered amusedly, "Abovegrounders. Utterly insane, all of you."