The first real day of the investigation started with a visit to the local police. Izuku got suited up and joined Aizawa and Tsukauchi in driving down to the police station. He thought he could've flown them there in no time with his new combination of Air Force and Float, but he was on a tight leash, according to Aizawa, so he had to follow his orders to the letter, which meant joining them in the car. It wasn't a sociable trio they were doing this run with, and Izuku wished All Might could've come with them, or even Gran Torino. The two of them got along like childhood friends, which Izuku supposed they kind of were — from All Might's perspective, anyway. Izuku had no idea how old Gran Torino was. At least seventy-five was his guess. As for his companions, Aizawa was as antisocial as they came, and Tsukauchi looked like he was deep in thought behind the steering wheel, and Izuku didn't want to distract him from either of those processes. He knew how important it was to get some time in your own head. Unfortunately, that left Izuku with his own thoughts, and the inside of his head wasn't as oiled a machine as it had once been, especially after what had happened last night.

Sankitsuo — if that was even his real name; it sounded like an alias now that he thought about it — was probably never going to give Izuku his blessing to use his Quirk, his meta-ability as he called it. With the almost supernatural control that the vestiges of One for All seemed to have over how the Quirk worked, it seemed likely that Fa Jin would never make itself available to him. It was a shame, because that Quirk, the power to build up kinetic energy with repeated movements and then unleash it in an explosive burst of power, would be invaluable if used in conjunction with One for All. Izuku had known the third user's Quirk for some time now, and had felt secure in the possibility — the slim possibility, as All Might said — that he never completely mastered One for All's basic super strength, because Fa Jin could level him out once he started using it. Once that power became available to him, there was no limit to how powerful he could be. Sankitsuo didn't approve of Izuku, though, and just last night had forbidden him from accessing his Fa Jin because they'd had a disagreement, and Izuku couldn't bring himself to be all too sad about it. If it was a matter of maintaining his moral standards or giving into Sankitsuo's twisted view on heroism and villainy, he wouldn't miss Fa Jin. He'd have to make do. He always did.

Izuku's thoughts were interrupted by Tsukauchi announcing that they'd arrived at the police station. The three of them climbed out of the car and took in the small building. It was two floors of the same kind of traditional architecture the rest of the town presented itself with. Tsukauchi made for the front entrance of the station, and Izuku went to follow him, but Aizawa grabbed him by the shoulder. Izuku looked back to see Aizawa gesturing with his head down the street, before he started walking, prompting Izuku to join him. As they walked, Aizawa explained.

"It's better if we split up for this. Tsukauchi is a one man army when it comes to information gathering within the system. As for us, we're better on the streets. While Tsukauchi gets as much info as he can from the police — records of unlawful construction, even legal projects that seem suspect in hindsight, that sort of thing — we'll be trying to get it out of them," Aizawa said.

"Them?" Izuku asked.

"Civilians. The rumours and fairy tales the people of this town are telling each other are about the Nomu, that's for sure. We need to find commonalities between them, the constants that never change from telling to telling. Those constants are what are likely to be factual sightings of Nomu that we can follow the trail of. You understand?" Aizawa elaborated.

"Yeah, I think I've got it," Izuku said.

There were only a few people on the street, and what few people there were steered clear of them, probably because of their costumes. Izuku suddenly remembered that Nagiso didn't have any active heroes. They had to know what heroes looked like, they had television, so were they just nervous? Izuku thought that was reasonable, as he was able to put himself in their shoes. If he lived in a relatively out of the way town, a village, really, and had never seen a hero — never even had a reason to see a hero — in his life, he'd probably be wary of two of them just popping up out of nowhere. After all, they did have television, so they had to know that heroes only went where there were problems for them to solve. If heroes had come to their small mountain town, then that meant there was something dangerous that had been here long before them, and that was definitely going to scare any adult, not to mention any small children they passed on the street. Izuku remembered his New Year's resolution, to give everyone he met a reason to smile, and put on a big grin to replace what he knew was probably an intense thinking face.

"What?" Aizawa asked, noting the change.

"Nothing. Just trying out a new thing," Izuku said.

"I've taken you on twice now partly because I thought you weren't like All Might. Smiling for no reason is pointless," Aizawa grumbled.

"And frowning for no reason isn't?" Smiling became easier as he poked at Aizawa a little bit. "Plus, I have a reason. It's something All Might learned from his master, and I want to put it into practice after speaking with her directly," Izuku said, pointing at his own head so that Aizawa got the message. "If someone needs a hero to save them, they're probably having one of the worst days of their life. So a true hero saves not only that person's life, but their spirit, too. If I'm smiling, then it tells people that I'm confident I can save them all. That's why I'm smiling."

"If you say so," Aizawa said, staring out at the street ahead of them.

Izuku looked around, trying to spot anyone they could casually approach and start a conversation with. He didn't want it to be an interrogation, as he didn't want to scare anyone away before they got what they needed, but they did also need something, so Izuku wanted to strike a balance between how aggressively he probed for information and how relaxed and casual he wanted the civilians to be. Izuku wished for what felt like the hundredth time that his friends could've come along. Not even because it would be more fun, but because all of them — Ochako and Hitoshi in particular — were infinitely better at talking to strangers than he was. Even Tsu, who was usually more reserved and only interjected when they thought they had something especially insightful or additive to say, and Katsuki, who'd sooner tell a civilian to kiss his boots than ask them for information, were better than Izuku at this part of the job. They'd had a grand total of one lesson on dealing with the celebrity aspect of being a hero, which Izuku had bombed. It had been cool to see their guest lecturer, Mt Lady up close — after Kamino, of course — since he'd actually seen her debut in person a little under two years ago now, but even adding her updated costume into his notebook didn't dull the pain of having frozen completely when a microphone and camera had been shoved in his face. Katsuki and Hitoshi had laughed. For a while.

"Come," Aizawa said, bringing Izuku out of his head.

Aizawa walked across the road, and Izuku followed. He tried to follow Aizawa's line of sight, but Izuku couldn't lock on to wherever it was that he was looking. Izuku guessed it was a technique that the near-unknown Eraserhead had picked up to do with his Quirk. Erasure was kind of given away if Aizawa was staring at one person in a chaotic battle, so he must have trained to be capable of keeping one target in his sights while making it appear as though he was looking somewhere else. Izuku would have to ask how he did that sometime in the future. They approached a man, seemingly an adult in plain clothes. The only notable thing about the stranger was his hair — he seemed to have some kind of porcupine mutation, so his hair was made out of sharp-looking needles. Izuku wondered if he could shoot them out or if they were just cosmetic.

"Stop," Aizawa said in a flat tone, already throwing Izuku's 'casual but firm' approach away entirely. "We have questions about a rumour going around."

The man stopped and looked shocked at Aizawa and Izuku's costumes. He studied the two of them for a moment before something clicked in his head. "Uh, sure. What do you want to know?" He spoke in a calm, but guarded way.

"We've been hearing a rumour about monsters in the mountains, and we're trying to separate fact from imagination. What do you know about these rumours?" Aizawa asked.

"Right, the sanpuku no kage."

"The what?" Izuku asked reflexively, and was suddenly unsure if Aizawa wanted him to interject, though it was too late to worry about that.

"That's what we call them, the shadows of the mountainside. Well, Yuki was supposedly the first to see them — Yuki Okita, that is — and the whole thing spread from there, so she'll probably have the most to say about it," the man said.

"And where can we find Yuki Okita?" Aizawa asked.

"Do you have a pen and paper?" the man asked in return, and Aizawa almost shook his head.

"I do," Izuku said as he brought out his notebook and a pen from his pack. Another handy Hatsume innovation. "What's that address?" he asked, flipping to the last page to write it in the corner. It hurt to write something not related to heroics in it, but he didn't have anything else.

The man told Izuku the address of this Yuki Okita, and he wrote it down quickly. Aizawa dismissed the stranger and kept on walking down the street, and Izuku tucked his writing utensils away. Sanpuku no kage. Shadows of the mountainside. These people had given the Nomu a name fitting for an urban legend or a boogeyman, but they weren't spooky stories at all. The Nomu were real, and they were dangerous. How long had they been around? At least weeks. The optimist in him hoped it would only turn out to be months. Years was the answer Izuku was afraid would come to light. They had to have only become active recently, though, because the news reports had started only weeks ago. Walking past the clusters of people on their way to work, running errands to the different shops on the streets they walked, and generally going about their lives, Izuku promised that he'd protect them as best he could. This was something valuable, and All for One's leftovers would not be the ones to end it.

As they walked around, Aizawa asked a few more people about sanpuku no kage, the shadows of the mountainside, and they all gave him the same answer, that a girl named Yuki Okita had been the first to see them a few months ago, and was never the same afterward. Izuku wondered just what she'd seen the Nomu doing, but figured he'd find out soon enough when they went to ask her all about it. Strangely enough, they weren't doing that just yet, and Izuku didn't know why. They had Okita's address, seemingly an up to date one judging from the fact that Aizawa asked everyone else they spoke to for an address as well, and there were no contradictions of that first address, so Izuku was getting a little bit confused about what exactly Aizawa's goal was.

That was, until he remembered what Aizawa had explained to him when they first started asking around. It wasn't just about finding some information and calling it a day, it was about asking everyone they could, even if every single one gave them the same story, and fact-checking that story using the other tellings as a kind of guide. If there was one detail that was different every time, like the colour of the beasts, that part of the story was probably further from reality than the rest. If one detail was the same every time, then that part of the story was likely closer to fact than to folklore. Izuku got it after that, and was able to be patient as they basically wandered the town asking random questions to random people. All of them who could remember where the story came from ended up pointing them toward Okita at the address the porcupine mutant had given them, so that was almost certainly where they'd get a lead.

Izuku felt a thrill rush through him as reality hit him at last, and he realised that he was conducting a real investigation as a kinda-real hero, and even following the scientific method, more or less. The scientific method was basically made up of three stages, at least as Izuku applied it: ask a question, come up with an answer based on what you already know, and then see if that answer is correct. Izuku did it every time he manifested a new Quirk, and this wasn't as different to that as he'd been expecting it to be. They'd asked the question: are there really Nomu here? They'd come up with their own answer: maybe. Now, they were testing their answer by compiling information to see if their conclusion was correct or if something else is going on. Izuku got a rush of energy from this realisation, and the smile came as easily as breathing after that.

Finally, as the sun was going down, they had as solid a story as they were going to get without going to the source. A few times, making sure he got Aizawa's permission first, Izuku turned Danger Sense's dial up to eleven — or eleven-thousand. He was able to get the whole town within his range, though at that kind of distance no danger would be detected. That didn't matter. He just needed a ping of something, anything out in those mountains, but there was nothing. It had worked during the joint training with 1-B, so why not now? Was it because the Nomu were brain-dead? Izuku had theorised before that Danger Sense worked by detecting the electrical impulses in someone's brain that flared right before they attacked and relaying that information to its user in that same instant. That was why it only worked on living things, Izuku guessed, and not inanimate objects that had no brain or will. The Nomu's brains didn't work right, they were dolls, puppets, so maybe their brain activity was low enough that they slipped right under Danger Sense's radar? But that wasn't completely right either. The Nomu Izuku had faced during his first internship with Aizawa, the Middle-Tier they'd fought all the way back then had triggered Danger Sense, so maybe some had higher brain activity than others? Izuku was starting to get freaked out by just how inhuman these creatures were turning out to be. No wonder Aizawa hadn't mentioned his old friend Shirakumo after Kamino. If one of Izuku's friends had been turned into one of those things like Oboro Shirakumo had been transformed into Kurogiri, then he wouldn't want to bring it up all the time either.

After the final attempt at sensing the Nomu with Danger Sense, Aizawa pulled out his phone and put the address they'd gotten into a map. It wasn't too far away, so they started their walk over. During that walk, Izuku thought about how he might go about asking how Aizawa was handling the whole revelation that Kurogiri was indeed his seemingly deceased childhood friend. Could he ask someone else to do it, someone he'd be more comfortable with? Izuku didn't really know how close Aizawa was to anyone, really, except for Midnight and Present Mic in an extroverts-adopting-an-introvert kind of way. Mic might have been a good place to start, since he was also close friends with Shirakumo. Midnight apparently knew the three of them back then as well. Izuku decided that, once this work study was over, he'd ask one of them. He knew there was something weighing on Aizawa, different from his usual bad mood, but wouldn't push it for now. The walk over to their final stop for the night was quiet, and Aizawa quickly and quietly used the eyedrops he seemed to carry everywhere when he must have thought Izuku wasn't looking. Had he used his Quirk at all that day? Izuku didn't know. Hopefully his dry-eye wasn't getting worse on its own.

The house was nothing special, the same kind of traditional style of construction as everything else in Nagiso. The lights were on inside, so people were home. They were likely either preparing for or just finishing up with dinner, which made Izuku feel bad for interrupting their mealtime, but he pushed that to the back of his mind. Aizawa knocked on the door, and it was only a few moments until someone answered the door. It was a woman, taller than Izuku but shorter than Aizawa, who had long, waist-length, straight brown hair and the same coloured eyes. She looked at Aizawa strangely, then took in Izuku's relatively bright and colourful costume, and seemed to realise that they were heroes.

"Hello?" she said, though it was clearly also a prompt to explain themselves. Izuku didn't think he would ever not experience the culture shock of these people having no clue why a hero would be around.

"Are you Yuki Okita?" Aizawa asked in return.

"No," the woman said, immediately leaning away from the two heroes. "That's my daughter. What business would you two have with an eight year old?"

Izuku's whole body tensed at hearing that. He could see a similar realisation on Aizawa's face, though he hid it well. Of course an eight year old had been terrified of a bunch of Nomu, and of course she'd thought they were ghosts or spirits. A pit formed in Izuku's stomach as he imagined what horror a little girl must have experienced if even trained heroes were terrified of Nomu. Izuku hadn't quite recovered from that shock when Aizawa powered through and continued speaking.

"We're here responding to the story she told about something she saw recently, something that might have frightened her," Aizawa said.

"The shadows. I'm familiar," the woman, presumably also named Okita, said. Her eyes narrowed, and she looked like she was holding something back.

"May we speak to your daughter? It might help our investigation into what exactly she saw if we could hear her experience directly," Aizawa asked.

"Of course. Please, come in," Okita said, and stepped aside to let them through the door.

The interior of the house was warm, compared to the winter chill that had been creeping up on them since the afternoon, so slowly that Izuku hadn't actually noticed he was cold until he stepped inside. He briefly wondered if he should take his shoes off, since it was tradition but they were also part of his hero costume, but when Aizawa didn't, Izuku figured he should follow his teacher's lead. Probing a little further into the house put them in a living room that looked strangely modern compared to the look of the house from the outside. They denied Okita's offer of tea. She looked at them strangely, like she was a little offended that they didn't want any of her tea, but then her gaze hung on their faces like she was studying them somehow. Izuku realised that, at least in regards to himself, her eyes were following the point-to-point pattern of the dotted scars on his face. They were mostly faded at this point, since it had been almost nine whole months since he'd gotten them during the USJ. He'd gotten lucky to survive the attack from Tenko Shimura that had given him the scars, but he forgot about them most days, just like he forgot that his hair was slowly turning white. Would Yuki Okita be frightened by them? Should they get someone else to talk to her? Were Izuku and Aizawa the wrong people for this part of the job?

"She mentioned that the shadows had big scars like that," Okita said, gesturing with a curve under one of her eyes, exactly where Aizawa's scar was. She looked at Izuku and gestured around her hairline, confirming his fear that she'd noticed his, too. "I don't want to be rude or anything, but is there a way you could cover them up?"

"Yeah, sure," Izuku said. He hadn't been wearing his costume's cowl, since he mostly put it on when he was actively putting on a persona, and he hadn't really been putting himself out there walking around with Aizawa, since his teacher had been doing most of the talking. Now, though, he figured it was the time, so he pulled the cowl up as he gave Okita a smile.

"Great, thanks!" Okita said with a smile of her own.

Okita then retreated to a back room, presumably to persuade her daughter to come talk to some strangers. While she was gone, Izuku recalled the fact that Nomu did in fact have grotesque scars all across their bodies. It was the result of whatever it was that All for One and his associates did to the people they once were to make them that way. It was hard to think that science could do that to a person. Izuku had almost convinced himself at one point that it was just having multiple Quirks that made their bodies mutate that way and becoming a Nomu was an unintended side-effect to the process, but no, it seemed that their physical mutation was intentional on the part of whoever it was that All for One recruited to help him create the monsters. Anger rose in Izuku's chest as he thought about just how sick a person had to be to put innocent people through that process, but calmed himself down before that little girl could see him. He wasn't going to give this girl any more reason to be afraid. If he could help it, no more sorrow would find its way into this home.

"Looks like you're taking point on this one, Nexus. I'll talk to the mother while you get what you can from the kid," Aizawa said, looking out a window at an angle that meant Yuki wouldn't see his face. Izuku's smile widened. The killjoy did care.

"She's eight, Eraser. You're talking like she's a suspect," Izuku said with a laugh.

Okita brought her daughter out and Izuku knelt before the girl as she sat on the sofa. Yuki looked just like her mother, only with bigger, wider eyes, like she was trying to take in as much as she could at all times. Her expression was detached, passive, like she was seeing everything but looking right past it at the same time. She looked over at her mother, who nodded to her with a strained smile, and Aizawa, who was pointedly not looking at her, and frowned. Yuki examined Izuku's costume, her frown more quizzical than upset, like she didn't understand what she was looking at. She looked down at his black leg padding, then his red arm braces, his weird, complicated gloves, and then stared up at his face. Her eyes stayed glued to the floppy, rabbit-esque ear-like tufts, and her face lit up with excitement, and she smiled so brightly that Izuku was stunned for a second.

"Are you a bunny man?" she asked so fast even Izuku, his circle's resident rambler, almost couldn't process the words. "Are you like Mirko? I really like Mirko. Are you her sidekick?"

"Uh, sure. I'm a bunny. I don't know Mirko, though. I wish. She's really cool, right?" Izuku said, making sure he smiled just as much as she did. The hero nerd in him needed to be held back from correcting the little girl on her Mirko facts, because the number five hero didn't have any sidekicks, but it wouldn't do any good to lecture the girl when she was clearly still dealing with something scary.

"Yeah!" Yuki said. She got up and did a few kicks at the air. "Her kicks are awesome!"

"I know! I do kicks, too, and I've actually copied a few moves from her," Izuku said, holding his hand over his mouth like he was telling her a secret. Her eyes widened like it was a massive conspiracy, and Izuku grinned at the sight.

"Can you show me?" she asked, staring at him like it was a perfectly reasonable request.

"Um, I'm not sure your mom would like it if I broke something. I'm pretty strong, y'see," Izuku said, glancing over at Okita and Aizawa, who'd started their own conversation off to the side.

"Oh," Yuki said, her arms limply hanging at her sides. It was like all the energy had been sucked out of her body in a single instant, and Izuku couldn't help but laugh at the kid.

"I'll tell you what, though — I'd like to ask you something, so how about I show you what I can do outside, after we talk for a bit. Is that okay?" Izuku asked.

"Okay! What do you want to talk about?" Yuki said, sitting back down on the sofa and kicking her feet against the deck.

Izuku took a deep breath, and hoped this wouldn't scare her off. "I've heard about some shadows on the mountains. Have you seen them?"

Yuki's expression immediately dropped into a frown, and her eyes widened in fear. She hunched her shoulders and curled her hands into fists, but didn't turn away from Izuku or try to get away from him or anything. Izuku made sure, even more importantly than when she'd been smiling, that now was the time that he smiled, because if not, then she'd think something was really wrong. It was, of course, but she didn't need to know that. Izuku kept his smile up and kept his eyes on her as he registered the conversation continuing between Okita and Aizawa on the other side of the room.

"It's okay. You're not in trouble or anything. I've just heard a lot about you from your friends today, so I wanted to talk to you. You're pretty famous, Yuki," Izuku said. He watched as her shoulders relaxed the tiniest amount, and figured that progress was progress. "What can you tell me about those shadows?"

"I …" Yuki looked over to her mother for guidance, seemingly. Okita came over to her daughter and sat beside her, wrapping her arm around Yuki's shoulders. It seemed to help, as Yuki relaxed completely into Okita's embrace. Izuku felt more than heard Aizawa's feather-light footsteps behind him.

"I saw them on my birthday," Yuki said, her voice shaking but strong.

"November third," Okita supplied.

Izuku kept his shock hidden, or at least he hoped he did. A whole month and a half before the news had gotten any hint of what was going on. They could've been hurting or killing people in the two months it had taken them to investigate.

"My party was over, and Komi and Toro—" Her friends, probably. "—had gone home. We were up at the castle—" Izuku remembered seeing something about a historical landmark just outside the town on one of the nearby mountains, the remains of a castle. "—and the shadow came out of the trees. It looked like a bird at first, but it was too big. It looked like a man, but he was dark, like a shadow. He had big scars all over, and I thought he needed help. I tried to talk to him, but he yelled at me. I got scared and ran away."

That definitely sounded like a Nomu, and one of the Upper-Tiers at that. Izuku's heart beat so hard that he was sure everyone else could hear it. Yuki had encountered one of the ones he wasn't certain he could beat. How did she get away, though? Every encounter Izuku had had with a Nomu told him they were relentless, and didn't stop chasing their prey until it was dead.

"What happened next? Did the shadow follow you?" Izuku asked.

"I don't think so. I went back to Mommy and we went home," Yuki said. Okita nodded along with her daughter's version of events.

"Have you seen the shadow since that day?" Izuku asked again.

"Nope. Now everyone's talking about it, though, and it isn't my fault! I didn't tell all of them, I swear!" Yuki said, wringing her hands like she thought she was in trouble.

"You're not in trouble, Yuki. I just want to know what really happened," Izuku said, forcing his smile to stay in place. He caught onto her wording, though, and wanted to frown. "Who did you tell?"

"Just Komi and Toro! But nobody else!" Yuki said, and her face was so serious that Izuku couldn't really take it seriously. Ironic.

"I believe you. Thank you for telling me," Izuku said. Yuki nodded quickly, and didn't really seem to be scared anymore, just confused about what exactly she had encountered. Izuku wasn't going to assume he was the cause of that, but it felt good to cheer her up somewhat anyway.

Izuku didn't think they were going to get any more information out of Yuki, so he looked up at Aizawa, and he seemed to get the message. He turned back to say goodbye, but Yuki was looking at him expectantly, like she was waiting for something, and Izuku remembered his promise. He'd said that he would show her what he could do if she cooperated. Izuku smiled, and an idea formed in his head so fast that he figured it was meant to be. He looked back at Yuki, who seemed to be so excited but trying to hide it, and leaned forward conspiratorially.

"Have you ever flown before?"

A few minutes later, after getting Yuki bundled up in her winter coat, Izuku had explained everything to Okita and how safe it was, and leapt into the sky with Yuki on his back. He hadn't used any of One for All in the hop, but he had allowed Float to carry them up, higher and higher, and put about five percent of One for All throughout his body Full Cowling style so that the flickering aura of green electrical discharge would light them up for Okita and Aizawa to keep track of them so high up in the night sky. Izuku subtly wrapped Blackwhip around Yuki's torso and legs like a harness as he carried her, and grinned as he heard her screams and whoops of joy. He let her enjoy a few minutes of flight, and brought her back down to the ground when he thought windchill and the risk of waking up any early sleepers should put an end to their little adventure. Once back on the ground, Yuki was ecstatic, and couldn't stop smiling. This time, Izuku thought he really had made an impact on her, and smiled just as brightly as she did.

"Thank you so much, sir!" Yuki said. She almost seemed to have stars in her eyes, as if she'd taken some from the sky when they'd been up there.

"Really, thank you. I haven't seen her this happy in a while. Oh, I forgot to ask. You heroes have special codenames, right? What do I call you?" Okita said with an identical grin. She looked a little teary eyed, too, at the sight of her child's happiness, which totally wasn't about to get Izuku going as well.

"My name is Nexus. I'm glad to help!" Izuku said.

Tsukauchi arrived to pick them up in his car shortly after that. His red eyes gave the impression that he hadn't slept in days, but Izuku knew that wasn't the case, because they'd seen him that morning and he'd been fine. He must have been pretty heavily invested in whatever research he'd been doing at the police station, and Izuku couldn't wait to find out what he'd found. On the ride back to the inn, Izuku couldn't stop smiling, even as they met back up with All Might and Gran Torino for dinner. He told the story of how the talk with Yuki and her mother had gone, and All Might nodded approvingly with a wide smile on his face. Izuku did not sleep that night feeling the weight of his argument with the third user of One for All. He slept easy, relieved by the contentedness of having helped a child feel better after a traumatising event. Dealing with Aizawa's kind of patronising rules during this work study was worth it after that.