OP. on AO3 under kai_mousy.

A/N: I forgot to publish this here, too. Sorry.

He first noticed it when his disciple grew a little more silent, and a worried frown showed up every time the adult thought he wasn't looking. Saitama wasn't much of a chatter, but he wasn't that much silent either. He sometimes engaged in small talk on where they were going to stay the night, or where they could get great deals and at what times to lessen expenses.

Some days, when the weather was nice and the blond was in a (growing more frequently by the day) good mood, Saitama would talk about the latest manga he'd read. Genos was sure the Doctor was the one providing them to his disciple, like the phone and credit card neither of them mentioned, but the teen did know about. Other days, when they had to go back to the lab and stay for a while, Saitama would humm silently and help the doctor with chores. Genos connected to tubes awaiting for upgrades to be finished.

Ever since Saitama came in, Genos' life started filling with the murmur of someone else moving around in the morning, words full of admiration and devotion after every battle, his own voice, recorded, sounding on the background as it was replayed over and over again at the end of the day.

So when two days went by in a row in an almost absolute silence on the adult's part (except for what strictly was necessary), Genos ran his scanners on his disciple for a complete diagnosis. But immediate results brought up a blank, so the cyborg decided to further investigate.

He got himself a journal, and started studying all patterns about his disciple. Meals, rest times, weight, height... Not even a small hair would lose the cyborg's analitical eye. Thankfully, Saitama didn't seem to mind or notice the extra attention. Which was another symptom to consider, since the man lived to get the blond's attention.

On the fourth day of his study, Genos concluded that it was possible their lifestyle was affecting the adult in some way. He talked with Dr. Kuseno over the phone, sending all the data he'd obtained, as well as physical samples to have a second opinion. It was no surprise, then, when the doctor backed his theory, pointing at how sendentary Saitama's life used to be until he met him.

Genos looked up from his cellphone to the man eating in front of him. There were bags under his eyes, but he wasn't exhausted at all; his gaze was fixed on his bowl, opposite to the usual staring to his sensei. He was an adult, yet, Saitama had deposited all his faith on a cyborg teen seeking revenge. It was clear he needed someone to look after him.

"Saitama," called Genos trying to shake the other out of his daze.

Saitama didn't answer, but looked up to the blond, acknowledging him with lazy attention. Genos noticed he didn't reach for the recorder. He considered his words before continuing. He wasn't sure how Saitama would take it were he to tackl the issue head-on; most people would denied it or be defensive on the matter...

"It's been over a year since you joined me in my quest," Saitama nodded in agreement, "and it's been some months now since we last had any lead on the Mad Cyborg," at this the brunette's eyes widened. Genos had never mentioned the Mad Cyborg before, but he knew the Doctor had put the cards on the table on the first week he met Saitama.

"Let's settle down."

"Sensei!?," Saitama rose to his feet in shock, which was a relief to the teen after several days of nothingness. "But what about your quest? Is it- Is it because I'm a burden to you, sensei?" A worried tone painted his question.

"Saitama, if you were a burden I would've let you at the lab to help the doctor. There are many factors that led me to take this desicion, the only one involved with you is your training," lied the cyborg, seeing the uneasiness in the brunette's eyes. That, however, seemed to calm Saitama down, who sat down again with a sigh.

"You've been doing well in your training, and I've noticed you do more repetitions than what I instruct," at this, Saitama's eyes shone with proud. "I think it's time you level up your routine, but to do so, you need a place to properly rest afterwards. And I need a place to not trouble Doctor Kuseno while I train myself."

"Sensei's so wise for his young age," whispered Saitama in admiration, before continuing out loud. "If it's ok with you, Genos-sensei, I can get the best deal to reduce expenses while we're settle down. If you have any preferences, please let me know, so I can look for that specifically!"

As expected, Saitama brighted up at the idea of being helpful to his sensei while being recognized by him. Genos nodded before finally taking his dish, and started eating as Saitama went back to his own food. If his usual frown was a little less prominent, Saitama didn't comment on it.

House-hunting with Saitama, turned out to be more complicated than Genos had initially thought. The teen was mostly alright with any kind of arrangement; money wasn't a problem at all, and after sleeping for so long on any kind of surface and in any kind of circumstances, either a luxurious or humble place were the same to the teen. Saitama didn't think so, though.

Genos had thought that given the frugal style his disciple had for living, finding a place would be easy, but they had already been to two different apartments and two houses in City D, and none of them passed Saitama's standars. They were either too expensive for Saitama to agree to live in, or they were not worthy enough for his sensei. Curiously enough, the brunette seemed to have selective hearing, since he ignored the cyborg whenever he said it was fine either way.

Genos tiredly sighed. They had been camping in D City's outskirts, so they checked the papers and online adds during breakfast before going house-hunting as soon as the first call came in. Now the sun was setting, they hadn't stopped for lunch, and Saitama was showing sings of fatigue. The man could be a force to reckon when it came down to deals. If it wasn't because his body was 90% mechanical, Genos was sure he'd be exhausted, too. They hadn't accomplish anything, but the teen was willing to admit it had been a good day.

He took a glance to his student; the sun shone on his hair, tired eyes fixed on the adds looking for more places. Genos lips curved into a small smile, the memory of his first day with Saitama coming to mind. Back then, the brunette was as tired as he was now and a lot more wounded, but he still had that same determined look.

"Stop frowning so much; you'll get wrinckles," said Genos ruffling the dark mop of hair.

"Wua-!," Saitama complained surprised and mild-annoyed by the action. "Sensei, don't do that, please, it's embarrassing coming from you. I'm an old man after all."

"Saitama, being twenty-three doesn't make you an old man; don't exaggerate. Now, it's getting late, and you haven't had a proper meal since breakfast, we'll continue tomorrow".

Saitama didn't answer, his whole body visibly relaxed, though. Genos counted that as a small victory and proposed they'd get some udon. Later, they'd do some more training, and a little fight to teach Saitama some moves wouldn't be bad. The brunette always cheered up whenever Genos decided to train with him. He'd surely be delighted to know they were going to fight for the very first time. Even Genos couldn't wait.

They were in a valley. It was far in the woods, between City D and City Z. The moon hung high in the sky, some stars just starting to shine, the clouds nowhere to be seen.

They had left their things closer to Z City, hoping to have better luck there the next day. Then, Genos had taken Saitama to the valley just to move better. He was aware the adult wouldn't move as fast as he himself did, and more probably not as widely either; but he knew better than to jeopardize the cities' safety.

Genos ran a scan on his disciple as he warmed up a few feet away. His physical strenght and general reflexes had increased more than he had anticipated. It'd be a lie if Genos said he wasn't proud of his disciple progress. The teen was aware he wasn't a very good master, but he started reading a lot about training and dieting for Saitama. The adult showed such a passion and humility for protecting people, Genos was amazed by him.

Saitama didn't pretend to be a saint, though. He honestly fought because he felt like it, because he wanted to, and he enjoyed saving people (and animals, if last week cat was something to go by). He was a real hero at heart, and if Genos could do something to make him an actual one for the rest of the world, well, he'd do it. He'd make the whole world recognize his extraordinary, virtuous disciple.

"Are you ready?," Genos called, readying his stance for battle.

"Yeah!" Came the excited answer. Genos had been right, this exercise was good for both of them.

"Remember, you must attack like this was a real battle. I have to evaluate what you know and are capable of." Saitama had a little bounce in his own stance. More due to eagerness than tecnique, but it made Genos smile. "We'll finish when one of us can't stand anymore," he instructed, waiting for his disciple's answer. "Now, come!"

Saitama ran towards him; his posture wasn't optimal to break through the air, but he was fast. He launched himself raising a fist, and Genos stepped sideway. Saitama fell forward, spiraling away due to the momentum. Genos took that chance to propel himself and land a descending kick to his disciple, to which Saitama barely had time to roll away from.

Genos let the brunette get up and attack again. This time, the adult tried to tackel the cyborg, only to be encircled by metal arms around his waist, and flipped through the air, landind on his side. Saitama got up again, gasping and sweating, a few scratches on his face.

"Don't rush without thinking," the teen instructed. "You have to analize your opponenet and think of a way to defeat it with as less injuries as possible."

"But Sensei just goes and figths!" Saitama pouted, lamenting his lack of recorder at hand. "You're always so brave and strong."

"It's not about strength. Remember you're fully human, and breakable. You won't be able to help others if you're dead," the teen answered. "Take care of you as much as you do of others. I can be rather easily repaired by Dr. Kuseno, even if I get cut in half. You don't."

That was hypocrite, and Genos knew it. All he wanted was strenght, power, to defeat the Mad Cyborg. But Saitama wasn't him. He didn't have to avenge his beloved ones, he didn't have a quest like Genos did. His drive was pure and kindhearted. Considering what he knew of this man, the life he'd had, Genos found him quite inocent; almost like a child wanting to be the hero because it's the right thing to do, and not because the glory and fame it could bring.

He had to protect that. Even from Saitama himself.

Saitama paused for a moment, panting. His eyes shone with emotion, almost like the day Genos happened upon him against that kaijin. There was a fire in those eyes back then that made the cyborg halt his interference and watch that (stupid or brave, Genos wasn't sure then) man fight to save the kid. Now he was proud to call him disciple, even if he hadn't said so out loud.

"For someone like you who has no firepower," Genos started, preparing to go on a full attack, "it's best to wait for the attack to come at you." At this, Genos propeled himself at full speed, barely giving Saitama enough time to see the next kick coming. "And use its impulse to deliver a more powerful attack!"

The adult hesitated a little and closed his eyes, readying for the impact, only to feel a rush of air make his clothes and hair rustle. Genos waited for him to open his eyes, his foot two inches away from the other's chest, a smile on his lips. When Saitama finally open his eyes a crack, the cyborg tapped his chest and lowered his foot.

"Think about that and practice your punches to counterattack. Remember you're fighting against wild beasts, not a dummy." Saitama's breath got caught and his eyes widened in awe. Genos shook his head amused, and turned to where they were now camping. "Come. It's already late and we have an early rise tomorrow; we'll continue once we're settle."

"Y-Yes! Genos-sensei!,"shouted the adult, jogging a little to catch up with the teen.

His disciple was in a better mood, Genos noticed, and that made the world a much better place to live in. It looked like he and Dr. Kuseno were right, and Saitama needed a more sedentary life, and Genos wasn't opposed to settle for a while, either.

Extra:

Saitama unlocked the door excited. It had taken some bargaining to get a good deal with rent, but they finally had a place. For some reason he'd manage to fed up Genos-sensei, and had to stick to the last apartment they visited, but he played all his cards to get the best of the place.

It was a small apartment in the middle of the abandoned part of City Z, just big enough to cramp two futons and few pieces of furniture in the main area. There also was a tiny bathroom, kitchen and balcony. That was it, but his sensei had said it was good enough, and left Saitama to deal with prices.

Now there they were, big travelbags on their backs, and a sole key for both of them to share. There was something exciting about living in one place with his sensei, the adult couldn't erase the silly smile that had set on his face.

A metallic hand on his shoulder shook him out of his reverie, and he looked back. Genos-sensei held his gaze for a moment, a small satisfied smile on his lips, as if he was saying 'good job' or 'well done', and Saitama felt his chest fill with pride. No matter what, Saitama swore he'd always make his young sensei proud of him... even if he ended up being bald, or if he never reached his sensei's level. He'd do anything for this incredible, wise, strong, and amazing teenager who had been through hell and rose up to avenge his family and bring justice.

"Go on," the cyborg said, and Saitama nodded enthusiastic. Then he finally opened the door and went past the threshold.

"Tadaima!"

This one stages what's going to be of next (and last) part. I find it hard to write from Genos' POV, so I'm sorry if it feels somewhat OOC.

Btw, I used the term Tadaima because I felt it fits better the sentiment for next part, so yeah.

Also, if you want to read something in next part, just leave it on the comments.