A/N: Hey everybody! Sorry it's taken me a hot second to update this, but I have been trying and failing to get this chapter to a place where I am happy with it and at this point I just decided to push it out so that I can move on to the next chapter.

A/N 2: As you may or may not have picked up, I am using songs that I feel capture my intended theme as chapter names, and will start putting in lyrics at the beginning of chapters to help communicate my intent.

Notes:

"Normal Speech"

'Internal Monologue'

"All Might/Yelling"

Chapter 2: How do I breathe

How do I breathe, without you here by my side?

How will I see, when your love brought me to the light?
Where do I go, when your heart's where I lay my head?
When you're not with me, how do I breathe?
How do I breathe?

How do I breathe - Mario

Tenya

After Alchemax had dismissed everyone for the day, Class 1-A had all returned to the classroom to retrieve their belongings. As he packed up his bag, Tenya noticed his brother wave him over to the teacher's lectern where the Pro Hero stood. As he arrived, Tensei gave him a goofy grin. "So, tell me, Mr. Iida," his brother asked in an exaggerated imitation of a reporter "what do you think of these new teachers at UA? Will they be able to go Plus Ultra and properly teach the students in the newly formed Class H-1?" Tensei then extended his hand out as though holding a microphone, wiggling his eyebrows with a goofy smile across his face.

Tenya smiled, then stood up straight, his chest puffed out. "Well, Reporter-san, I can assure you that they will be splendid and wonderful additions to the staff. This is especially since my own beloved brother will be one of the new persons who will be instructing here!" Tenya replied, "I look forward to the expansion of my own education here at this prestigious and august place of higher learning and am certain that –" His response was interrupted by his elder brother dropping his extended hand to slap his own armored knee, his body shaking with laughter.

"You don't need to be so serious, Tenya! Seriously, I keep telling you to loosen up!" he snickered. Tenya frowned. As much as he loved and admired his brother, this part of his personality had always rubbed the young Engine quirk user the wrong way. For all their similarities in terms of appearance, quirk, and intelligence, Tenya and his brother had always been polar opposites in temperament. Where Tenya prided himself on being polite, formal, and respectful, Tensei Onii-sama was irreverent, casual, and playful. "There is nothing wrong with being well-spoken!" he huffed, vexed that his own brother would make light of him.

Tensei looked at him fondly "Now, now! Let's turn that frown upside down, sourpuss! Come on, why don't you introduce me to these new friends of yours. I think they were Midoriya-kun and Uraraka-san?"

Tenya smiled and nodded, more than happy to introduce his favorite person to his friends. He grabbed his brother by the arm and dragged him over to his friends, who had been polite enough to wait for him. "Midoriya-kun! Uraraka-san! I would like to meet my elder brother, Tensei!" Tenya beamed. Uraraka began giggling at the sight of Tensei being dragged in Tenya's wake, while Midoriya had set his bag down and began shuffling through it feverishly. After a few moments, the verdette student extracted a notebook marked Hero Analysis for the Future Vol. 9 and marker from his backpack and flipped it open.

"Omigodthatsrightcanyousignthispleaseingenium" Midoriya blurted out, holding out the notebook. Said notebook, Tenya noticed, was open to an analysis of Tensei. Across from a detailed drawing of his elder brother in his costume, Tenya saw notes on said hero costume, his quirk, and even notes pondering whether Tensei would need to go to a mechanic or to a surgeon should he ever need to have elbow surgery. From the overlapping notes that were written in various shades of ink and pencil, the entry had been updated over time. Uraraka-san's giggling had grown louder at Midoriya-kun's display, and Tenya couldn't help but join in the moment of levity as his brother took the notebook and signed it, a bemused look on the Pro Hero's face. After signing it, Tensei began reading the notes Midoriya-kun had written, occasionally nodding, and smiling. When he did hand it back, Tensei clapped Tenya on his back. "You weren't kidding, Tenya, Midoriya-kun really is a talented Quirk analyst!"

Tenya nodded, rubbing the now sore spot his brother had hit. "Of course, I wasn't kidding, Onii-sama! In the short time that I have known him, Midoriya-kun has shown himself to be intelligent, kind, and resourceful. That's not even to mention how he singlehandedly defeated a Zero-pointer during the Entrance Exam." Tensei's jaw dropped at the last part, as surprised as Tenya had been to hear of the feat.

"That was you? Pardon my language, but holy shit kid! I remember 'Zashi and Nem telling us newbie teachers about it when they were telling us about Class 1-A, but I thought they were just blowing smoke!" Ingenium exclaimed.

Midoriya began to blush, clearly embarrassed to be praised like this, though Tenya didn't necessarily understand why; if you did something that was righteous and heroic, what is there to be embarrassed about. "I-it's wasn't really that much…" he murmured.

"Yes, it was, Deku-kun!" Uraraka protested," You saw that the Zero Pointer was going to squish me and you jumped in to save me without any hesitation! If that ain't heroic, I don't know what is!" Tenya and Tensei nodded in agreement. "Sounds pretty heroic to me." the elder Iida brother remarked. "Also, Deku? Weird nickname to give to a friend. Doesn't that mean 'useless'?" He added, a concerned look on his face.

Uraraka snorted, a bit annoyed that the original meaning of the name was brought up. Granted, anything that forced mentioning that unlikeable brute Bakugo into a conversation was an easy way to sour the mood. "Actually, it's a shortening of 'dekiru'. Y'know, meaning 'you can do it!'" the brunette girl clarified.

Midoriya nodded, a faint blush on his face. "Y-yeah, Uraraka called me that my first day here at UA, and it kinda…stuck."

Tensei nodded in understanding, then shrugged. "Well, whatever. Anyways, Tenya and I were going to head home. Since I brought my car, why don't I give you both a ride, at least to the train station?" Both Midoriya-san and Uraraka-san agreed and thanked Tensei for his offer, and the four of them made their way out of the building. As they walked, Izuku inundated Tensei with questions about his work as a Pro Hero, as did Uraraka-san. Tenya knew that he was by far his brother's biggest fan, but it warmed his heart to hear how much his new friends also admired his elder brother.

"A-also, Ingenium-sensei, who are 'Zashi and Nem?" Midoriya asked, confused.

"Oh, sorry. I meant Present Mic and Midnight." Ingenium clarified. "As Alchemax-sensei had mentioned, the five of us went to UA around the same time; Alchemax went here as a member of the Support Course, and the rest of us attended in the Hero Course."

"I see!" Uraraka said, before looking confused "Wait, then how is he a Hero?"

Tensei gave a bemused smile. "Due to how his quirk works, Ameya figured the things he would learn in the support course were integral to becoming a hero, so he applied and got accepted into both the Hero Course and the Support Course. He asked Principal Nezu to be enrolled in Support but be allowed to audit Hero Course classes. The deal was he could do so if he could successfully pass whatever classes he would miss due to the overlap. The Heroics teacher at the time agreed and graded him as though he were enrolled."

"Wow! He must be really diligent then." Midoriya murmured.

"Yep! He was basically running off coffee and cup noodles the entirety of our time here at UA, but he was able to graduate with a double certification in Heroics and Support." Tensei grinned. "He is one of the very few people our age who is a fully licensed Hero and Support Technician. Unfortunately, the HPSC caught wind of this and forced Principal Nezu to no longer allow students to multi-track."

As their happy quartet made their way to the staff parking lot, Tenya's attention to the conversation between his brother and his friends faded as he took in his surroundings. On the pathway ahead of him, he saw clusters of students making their way toward the giant front gates of UA. As they passed, Tenya was able to pick out some groups he recognized, like that of Kirishima, Kaminari, Ashido, and Sero, as well as some combinations of students he hadn't expected to see, like the quiet 1-B girl Kinoko Komori and her classmate Ibara Shiozaki. Leaning against the gate in the distance, Tenya recognized the short purple bob of Jirou-san and the ginger side ponytail of the Class 1-B representative, Itsuka Kendo. However, Tenya's carefree train of thought came to a screeching halt when he saw her standing there with Jirou-san and Kendou-san.

She stood with her back to them, her beautiful, silky black hair schooled into a perfect spiral ponytail, somehow both perfect and effortless. The pale nape of her long and graceful neck bridged the gap from hair to the collar of her grey blazer. Under that blazer her figure, curvy and feminine, beckoned his eyes toward a slender waist he longed to wrap his arms around, and her womanly hips flared out beneath her blue-green pleated skirt only to return to her supple, long legs enrobed in knee socks. The hourglass of her figure was further emphasized by her height, as she stood nearly 10 cm taller than her friends. Looking as beautiful now as she had been the first time he saw her, not as a friend but as a woman, was Momo. 'No, not Momo,' he chided himself. 'Yaoyorozu-san. You lost the right to call her by her first name a long time ago. And you definitely lost your right to be near her when you started to look at her with such lascivious intent. For goodness' sake, Tenya Iida, you leer at her with the same lust as Mineta-kun did!'

At that moment, Tensei looked up from the conversation he was carrying with Midoriya-kun and Uraraka-san and also spotted her. He quickly shot a glance at Tenya, who met his brother's gaze. Despite knowing it was not their family's quirk, Tenya telepathically begged his brother to understand that Tensei should not call out to engage Yaoyorozu. Tensei met Tenya's gaze and nodded. Then, his brother put on a friendly smile as he turned to face her. "Yaoyorozu-chan! Fancy seeing you here! I thought you would have left already." Tensei called, walking towards the target of Tenya's crush and her friends.

Tenya was floored. 'How could you, Onii-sama?! Clearly, you saw I wanted you to steer us clear of talking to them, didn't you?' the bluenette screamed in his mind. Unfortunately, there was no time to determine whether the collision course Tensei had put him on was due to miscommunication or willful malice; Tensei's calling out to her meant Momo now saw Tenya. For just a moment, her eyes shined with…something, before she morphed her surprise into a friendly, soft smile.

"Te- er, Iida-san." she said.

Hearing even a fragment of his first name come from her made Tenya all too aware that he called her Momo in his mind, and likely would have called her such out loud. Granted, it didn't matter what he would have called her, since at the moment he somehow found himself unable to breathe. 'Oh goodness, what do I do? What do I say?' he panicked. Forcefully, Tenya schooled his expression to one of respectful friendliness and approached his vice-representative alongside his friends.

"Greetings, Tensei Onii-sama!" Yaoyorozu-san smiled. "and greetings to you as well, Midoriya-kun and Uraraka-san! I was waiting for Ameya Onii-sama to come from the staff room; according to Cementoss-sensei, there was a package of some kind he needed to sign for, and Ameya Onii-sama told me to wait for him. Jirou-san and Kendou-san decided to keep me company until he returns." Greetings were exchanged between all parties, and Tensei introduced himself to Kendou-san. The group chatted for a few minutes until Tensei shot a glance at Tenya and smirked. 'Oh no, I know that expression. Onii-sama, what are you about to do?' the blunette speedster student worried.

"So, tell me, Momo-chan, what's new with you? Do you have a boyfriend yet?" Tensei asked. Tenya froze, his chest suddenly tightening. What if Momo was dating someone? Up until this point, Tenya had been careful to keep his distance but what if, in his rush to avoid making Momo hate him, he had unwittingly given someone else an opening?

Fortunately, his fears were laid to rest when Momo had turned scarlet and shook her head violently. "N-no, I have no one like that in my life!" she responded quickly. Tenya felt relief wash over him, but at the same time, he was filled with…chagrin? What were these feelings? Why did the idea that Momo was in a relationship bother him so much?

While this intense internal conversation was happening, Tenya was standing rigidly, staring off into the space just above Yaoyorozu's head. Midoriya stood beside him, the verdette unsure as to whether he should rouse his friend from his trance. Before he could, however, Ingenium nudged Tenya out of his reverie as Alchemax-sensei arrived, one of the UA service robots following him. The robot was pushing a dolly cart with a large metallic crate on it.

"Heya Tensei, look what arrived!" Alchemax crowed loudly, tapping the box with the talons of his glove. Tensei smiled and helped Alchemax take the crate off the dolly. After bidding the robot operating the dolly to return to the Support lab, Alchemax turned to the students that now stood in anticipation, clearly interested in what lay within the box.

"Want to see something cool?" he asked, an excited grin on his face. Opening the lid of the crate, the swarthy hero began to pull out a large khaki tarp, which he laid down on the ground. This was followed by various geometrically shaped solids. The pieces were of numerous different materials, including steel, rubber, and aluminum. Tensei looked at the blocks blankly for a moment. After the final block, which was made of a dull green plastic, was placed on the tarp, Tensei's eyes widen with understanding. The speedster began laughing and shaking his head.

"Of course, you would insist on bringing it with you, you gearhead!" the elder Iida brother snickered. "Gather round, everyone, this is going to be really cool."

"What is he going to do?" Uraraka asked, a curious look on her face. Midoriya nodded, pulling out his notebook to write down everything he saw. In the distance, Present Mic was seen walking toward the parking lot, before making a sharp turn and running full pelt to stand by Tensei's side.

"Oh man, is he doing it?" The Voice Hero exclaimed, his voice loud enough to be grating on Jirou's sensitive ears.

"Yeah! After all," Ingenium said, "If there is one thing Ameya love doing, it's putting on a show."

Shooting his fellow teacher a glare, albeit one without much fire, Alchemax motioned for everyone to give him space. Then, he extended his hands, closed his eyes, and began to concentrate.

After a moment, the hero's eyes shot open, the dull gold of his irises now spreading to cover the entirety of his eyes. The blocks themselves began to glow with a golden aura as well and soon began to also vibrate softly. Grinning, Alchemax began to make sweeping waves of his arms, hands, and fingers, extending and flexing as though playing a gigantic instrument. As he did, the blocks began to dissolve like sand. The now-dissolved material rose and flowed through the air against gravity as though following invisible paths. Slowly, the materials merged, occasionally flashing brightly before the aura returned to its' original golden hue.

The display caught the attention of not just the six students who had gathered near Ingenium and Present Mic, but the other students who were making their way home. Soon, a crowd had gathered around the hero, as the floating items began to turn into recognizable shapes. Kendou in particular was enthralled. After a few moments, she gasped, finally realizing what was being formed. Before she could verbalize what the Alchemist Hero was doing to the others in the crowd, however, the floating pieces connected to one another, before being gently lowered onto the tarp. When the golden glow dissipated, in the place of the various blocks of material stood an olive drab touring motorcycle in pristine condition.

"You really couldn't resist bringing Laila with you, huh?" the speedster hero laughed. The Voice Hero was similarly in a good mood, before making eye contact with Alchemax.

"Can I, Ameya?" Present Mic pleaded, pulling a small index card out of his pocket.

Ameya Onii-sama chuckled and rolled his eyes. "If you must."

Clearing his throat, Present Mic took a deep breath. "The Alchemist Hero, Alchemax!" he shouted, his voice carrying to the students who were on the outskirts of the crowd, "His quirk, Matter Manipulation! He can manipulate matter at the molecular level, allowing him to turn just about anything into anything else."

Midoriya's eyes widened. "That's why his name sounded familiar!" Midoriya exclaimed. "Alchemax is the Number Seven Hero in India! I had no idea he was part Japanese, let alone that he was related to Yaoyorozu-san!"

There was a pause before the entire crowd broke out into uproarious cheering. The Alchemist Hero just waved graciously, before pulling a motorcycle helmet out of the crate and throwing a leg over the motorcycle. Finally, his eyes glowed gold once again, and as he moved the fingers on his right hand, the solid wooden crate dissolved like the blocks had, then turned into an amber liquid. Alchemax unscrewed the gas cap to the motorcycle and guided the liquid, which now was clearly fuel, into the tank. Screwing the cap shut, Alchemax started the motorcycle, which roared to life.

"Oh, yeah…" The hero purred huskily to the motorcycle, a child-like grin on his face. "You okay with getting a ride home with me instead of waiting for your driver?" The hero asked, turning to his cousin. The heiress returned the hero's smile, before lifting her shift. From her toned and flat stomach came a pink glow, followed by a red motorcycle helmet. "Of course, Onii-sama!" Yaoyorozu chirped as she sat down on the back of the motorcycle behind the hero. "I will let Matsuda-san know, of course." Nodding in agreement then putting on his own helmet, Alchemax waved the crowd to clear a path, after which he, and his cousin, drove off through the main gate of UA and onward.

Slowly, the crowd dispersed, including Present Mic. This left just the five students and Ingenium.

"Oh. My. God." Jirou whispered, "That was so rocking!" Kendou nodded in disbelief, also taken in by what she had just seen.

"Did you see the motorcycle? He just… created a motorcycle!" the ginger girl said, still clearly stunned by the display.

"Yup," Ingenium grinned. "Ameya is pretty laid-back, but his quirk is no joke. I have no doubt that if he had chosen to stay here, he would be a Top Five Hero. Heck, he might even be the Number Two Hero."

This caught everyone's attention. "Whoa, he's that strong?" Uraraka-san exclaimed.

"Eh, maybe not stronger," Tensei hummed, "but he's a whole lot more likable than Endeavor." This information was being furiously written into a new entry in Midoriya's notebook, alongside a variety of questions.

Eventually, Jirou and Kendou bid their classmates goodbye and left, and Ingenium, Iida, Uraraka, and Midoriya made their way to the Turbo Hero's car, and then to the station to drop the two who were not members of the Iida family off.

After the car only contained Tenya and his brother, Tensei turned to him. "So," Tenya's elder brother muttered. "We are going to talk about whatever is going on between you and her, understand." Tenya gulped, then nodded. Maybe talking about it would put his mind at ease, right?

"Oh, but before I forget, we are going to have a guest over tonight, so please called Dad and ask him to be home for dinner."

Tenya looked at his brother inquisitively. "Who is coming over?"

Tensei smirked. "Your future sister-in-law."

Tenya balked. "Wait, who?!"

A/N: And that's a wrap on Chapter 2! Hopefully, Ameya's quirk is not too powerful (although, your opinion on that will likely change if this fic lasts long enough to go where I want it to go). Also, hope that my prose didn't come off as too dense. Other than that, have a great day, and thanks for reading!

Next time on My Hero Academia Substitutes: Rumi meets her in-laws.