Chapter 1: The Argument:

Author's Note: Hiii everyone! I know I haven't been updating like I usually do but, that is for the simple fact that I'm in Virginia on a one week vacation so I haven't picked up my laptop like I've wanted to.

On another note. Me and cuddlySoldier and another author have been working on a great pieces for Osomatsu-san while I'm still waiting for more ideas and summaries for fanfics that I will update and finish.

Story Summary: Choromatsu has finally had it with Osomatsu's irresponsible self and finally he tells the eldest Matsuno sextuplet his thoughts on it all. But, what happens when an unexpected accident happens and leaves him and Karamatsu as the eldest brothers for awhile?

Disclaimer: I don't own anything. All credit goes to the original owners.

ENJOY THE STORY!

Todomatsu walked into his house after a long day at work, and expected to see his shitty no good brothers just lazing on the floor the whole time. But, what he saw instead was a scene he never wanted to see again in his life.

Choromatsu and Osomatsu were glaring at each other as Karamatsu stood in the middle attempting to pacify whatever situation was going on between the third and first sons. Ichimatsu was attempting to keep Jyushimatsu calm, for it seemed the fifth son was close to breaking down the longer the fight dragged on.

"You shitty eldest brother!" Choromatsu yelled as he pushed against Karamatsu's firm hand that pushed against his chest, each time he tried to get closer to the other who seemed just as determined to get to the other the moment he could. "Why can't you just grow the fuck up?!"

"You shitty younger brother!" Osomatsu yelled back, hands curling into fists. "You think you're any damn better? All you fucking do is say you're looking for a job but, behind the job circular, you're goddamn fapping off to some idol shit! You hypocritical, tight-assed, virgin NEET!"

The room fell silent, save for Osomatsu harsh pants as he tried to regain his lost breath from screaming.

"..." Choromatsu stared at the older in shock. "...I hate you… In truth I think we all hate you!"

Todomatsu felt his stomach fall into his feet keeping him firmly grounded to the floor. His throat was suddenly dry as he watched his two older brothers fight, he's seen them fight with each other before, Hell, he was in most of those fights. But, they never escalated this badly.

In fact it seemed that those three words, were the words for Osomatsu to finally snap. His eyes narrowed in apparent anger, he stomped out of the house, pushing past Todomatsu like he wasn't even there.

The minute the door closed, Todomatsu fell to his knees, and a loud piercing wail hit the quiet air as the tension eased and Choromatsu slumped to the floor seemingly exhausted.

"You shouldn't have said that…." Todomatsu murmured dazedly as he looked at his older brother eyes confused. "Why would you say that?"

"What possessed you to say that Choromatsu-niisan?" Jyushimatsu wailed as he cried into Ichimatsu's shoulder, while Karamatsu took the other side to comfort the distraught sextuplet. "We all love each other…"

"You always think you're better than the rest of us…" Ichimatsu mumbled quietly, as he continued to pet Jyushimatsu's hair.

"I….I…." Choromatsu was at a lost for words. "I didn't want him to leave… I just didn't want him to say… to say the…."

"The truth?" Karamatsu spat looking at Choromatsu angrily. "You have to stop lying when it comes to things like this and instead of yelling hurtful things like that to Aniki, you could have waited until he cooled off."

Ever since Osomatsu's near suicide incident, Karamatsu had been even more protective than before. He was always ready to help Osomatsu when he needed it and always enjoyed spending time with the other eldest in the household.

"But…" Choromatsu began, before he was cut off by Todomatsu.

"What started the argument?" The youngest questioned glancing around for an answer. Jyushimatsu averted his eyes, making his own doe eyes narrow down on the fifth child. Jyushimatsu was always bad at keeping secrets anyway. "Jyushimatsu-niisan, do you have an answer?"

The yellow-Matsuno flinched back and he buried his face into Ichimatsu's shirt, the trashy feeling Matsuno rubbed his back comfortingly, while Choromatsu glared at Jyushimatsu's back and Karamatsu smacked the third eldest on the back of the head.

"Jyushimatsu-niisan, tell me what happened." Todomatsu said in a dead serious voice. "Or, I'll tell everyone what you said you felt about Ichimatsu-niisan last week."

Jyushimatsu's face turned red as he looked at Todomatsu, fear and anxiety clear on his face. He shook his head as confliction flashed across his face as he looked at his brother.

"T-The…" He began his usually steady voice shaking slightly. "The argument was about…"

Ichimatsu lightly rubbed the younger Matsuno's back in a comforting kind of way, making the other relax slightly.

"They were arguing about Osomatsu-niisan's position as older brother." He finished quietly, as he curled in on himself a bit. "Please don't be mad at me Choro-"

He was cut off as Choromatsu angrily slapped him across the face. The usually sunny smile was off his face and he was crying harshly, his left cheek had a red welt on it.

"You shouldn't have said anything Jyushimatsu!" Choromatsu said, face red with anger. Karamatsu quickly restrained the third eldest and dragged him after from the youngest trio.

"And you shouldn't have hit him!" Todomatsu shot back, as Ichimatsu growled low in his throat.

The door shut at his last remark.

That night at dinner, Osomatsu never came home and nobody talked at the table either. But, they all had one thing running through their heads.

'Where's Osomatsu-niisan?' Ichimatsu thought as he looked around the room.

(A/N: They're using that system they used in episode 23 where they were communicating without actually talking.)

'I wish I knew…' Todomatsu thought cast Choromatsu a dark glance. The third brother looked at his beef stew which tasted bitter in his mouth.

'I hope he's okay…' Choromatsu thought glancing around at all his brothers. 'I didn't mean it… I was just so mad…'

The room was chilly and silent as the brothers all stared at each other. Their mother walked into the room, hands placed onto her chest in a concerned fashion.

"Jyushimatsu." She spoke in a soft voice, as her fifth son looked up at her curiously. "Doctor Dekapan is on the phone for you."

The yellow parka wearing brother made his way to the living room, he saw the phone lying on it's side, waiting for him to pick it up.

"Hai, Jyushimatsu here." He said into the phone, his tone not as cheery as it usually was.

"Ah, Jyushimatsu, I have your brother Osomatsu-san here." The old doctors voice replied back to him. "I need you or some other brother to come and collect him."

The fifth child made a noise of affirmation before a question popped into his usually blank head. He made a confused noise as he waited for the doctor's own confirmation that he could ask the question.

"Why can't Osomatsu-niisan just come back by himself?" He found himself saying, without thinking of a better way of saying it.

"There was an… accident, with one of my latest experiments and your brother got caught in the middle of the cross fire, so he needs someone to come pick him up please, hoi." Jyushimatsu felt his heart freeze in his chest.

"I'll be there in a moment." He murmured hastily into the phone as he quickly hung up to go and get his slippers on.

Without even glancing at his brothers, he was out the door ignoring their confused voices calling out for him to stop and answer them.

Arriving at Dekapan's Office in record time, he entered the establishment with a murmur of hurried greetings.

"Dekapan-hakase, where's my brother?" He asked, praying to every god, even Kamimatsu, that his dear eldest brother was okay.

"One second, hoi." The kind man said as he went to another part of the office. "Come on out, no one's going to hurt you… Jyushimatsu's here like I promised."

The meek shuffle of feet a few minutes later, showed the man had been successful in get his brother to come out.

Jyushimatsu felt his smile freeze on his face and then fall at what he saw in front of him. Standing there in a big red hoodie and a sleeve covered hand in Dekapan's was his older brother, who was now somewhere between four or five.

"What… happened to him?" Jyushimatsu questioned quietly, as he kneeled down in front of the smaller Matsuno careful not to startle him.

"Like I said, there was an accident, hoi." The old man replied. "He reverted to the state of a four or five year-old. He also doesn't seem to remember anything about his life, so I told him he had five older brothers. I told him you were going to come and get him, so he was expecting you."

"A-Are you m-my older brother?" The shy question hit the air and Jyushimatsu's head snapped back to the now child Osomatsu.

'This must be before we were troublemakers of Akatsuka Town.' He thought remember when they all phased through the shy personality before finding their place in the town.

"Yeah, I'm Jyushimatsu." He answered picking the child up. Osomatsu laughed briefly as the physically older brother, spun him gently before placing him on his shoulders.

The five year-old (A/N: I've decided on five for his age.) leaned against the slightly messy hair and began to fiddle with it, gently plucking the single cowlick on his head making him laugh.

"I'll be taking him home now." Jyushimatsu said as he looked at Dekapan nodded.

"I've already informed your mother, hoi."The older male said as he began to pack up his office. "She should have somethings read for your brother when you come home."

He nodded in understanding before standing, and bowing, making the child hold onto his head as to not tumble off.

"Thank you for holding him until now, and sorry for the trouble he probably caused before the accident." He apologized for his older brother like usual.

"Ah, he didn't cause trouble," The man corrected. "In fact I should be apologizing."

"What exactly happened anyway?" He asked standing upright and wincing when Osomatsu clutched his hair as he fell slightly backwards.

"Well, I was working on a age reducer pill, when Osomatsu-kun came in here looking upset." He began, as he arranged some medicine in a cabinet. "I offered him an ear and a cup of tea and he accepted."

Jyushimatsu swung the child back and forth on his oversized sleeves before throwing him up and catching him easily, making the adult turned child laugh childishly.

"I was going to test the pill on myself but, I ended up putting it into Osomatsu-kun's tea instead of my own… so this in reality is my fault…" The man ended with a quiet sight. "I'm really sorry Jyushimatsu-kun."

Jyushimatsu shook his head, as his hands continued to occupy the child relentlessly tickling him every now and then before moving out of grabby hands way, subconsciously as he looked at the doctor eyes serious and concerned.

"It's fine." He murmured. "Just please look for a way to reverse the effects."

The good doctor nodded, and Jyushimatsu bid him a goodnight before heading on his way.

'How am I supposed to explain this to the others now?' He thought as the child in his arms looked at all the sights in front of him and around with wide sparkling eyes. 'Man, things just went from bad to worst…'

Author's Note: Yay! Chapter 1 done! I'm going to continue this story along with my other stories. It's so much fun working with AU's for Osomatsu-san.

Don't forget to read and review. This story along with all of my other Osomatsu-san stories are on Archives of Our Own.

Bye-Bii!