I'd write my own summary here, but you should understand that for Japanese fanfics, much like their light novels, the title often IS the summary.
This work differs slightly from the original. It has been edited for content, and formatted to… okay not really.
Disclaimer: I didn't write anything you see here, 'kay? By the way, just mentioning this in passing, but some guy 「うみがめ」 wrote a collection of one-shots somewhere. If you don't get what I mean then please refer to the start of some of my previous 'works'.
Title (One-shot): When Isshiki is given the younger sister treatment, their reaction is…
[Hikigaya Hachiman POV]
After school, in the student council room.
"I was wondering, Senpai, but is it really true you're a siscon?"
Today, I was routinely helping Isshiki out with student council duties, when she suddenly asked this question.
"It's not 'Nna' here is it, Yui-senpai made it clear that she believes senpai is undeniably a siscon, but is it true?"
Siscon, huh? I could flat out reject the accusation, but, well, if I had to answer… objectively speaking, it's true that I do love Komachi – it goes without saying that it'd be impossible for me to NOT love the world's number one younger sister – but, siscon? Hm. That line just now… well, for now I'll just go with yes.
"Hmm… that might be somewhat the case?"
"Mm. 'Siscon?' - If I was forced to answer honestly, it would seem that way."
"Re-aally!? Then, today, for one day, please treat me as if I were your younger sister!"
What is this person talking about?
Is it that? Did the constant hectic nature of student council work finally affect her head?
This request, isn't it too unnatural?
Well, certainly this kouhai of mine does give me more of that imouto-like feeling rather than that of a regular underclassman, but regardless, no matter how you see it, in the end the reality is different.
"It's not 'hah' here either. If it's a siscon, anything in the direction of having additional younger sisters would be favourable, right? Besides, it's the case that I'm an only child, you knowww?"
"You say 'I'm an only child you knowww' like it's completely obvious, but that's not something I had any prior knowledge of."
"Huh? Did I really not say so before? That I'm a single child, but have a longing for an older brother? That's whyy, it's a give and take!"
"Haah… even following that line of reasoning, just why would the one acting as your older brother have to be me? That kind of conclusion makes no sense at all, don't you think?"
"That's obviously because, if it's older people around me, except for senpai there isn't really anyone else, is there?"
"There's Hayama and Tobe, you know?"
"Haaah. Senpai, come on, you could at least have a proper think before asking unnecessary questions. Neither of those two have any hands-on experience in being an older brother, isn't it obvious?
THAT. IS. WHY, it has to be you, senpai, now I've proved my point, so please become my older brother for today."
As she said this, Isshiki brought her hands together in front of her face and pleaded… well, as she normally does.
Right. As if that kind of cute appeal would still have any effect on me. Don't make light of the unshakeable resolve of your elders, Isshiki! This unreasonable request, I'll shut it down!
"… hah, I understand. Just for today. But be aware that I won't be doing anything that's too troublesome, Isshiki."
… Who am I kidding. That unfair technique, it's not something I can muster enough willpower to refuse, and she knows it.
"As expected of senpai!"
"...So. What exactly is it that I should I be doing, then?"
"Right well, now that senpai has become my onii-chan, the basic step would be to call me directly by name."
"Nn? Senpai, when it comes to talking with Komachi-chan, what name do you call her by?"
"Since that's so, then I'd like the same treatment - 「Iroha」, please use my first name!"
…Indeed. Certainly, for a younger sister, it would be natural to address them by their given name, without any need for honorifics.
That's why, in this situation, to also call Isshiki 「Iroha」 would only be the appropriate thing to do, and perfectly natural… waait, just how did I end up with this conclusion!?
…In the first place, this person isn't even my real sister to begin with!
The one and only younger sister I have is Komachi!
"Senpai… is it… no good…?"
"YES! What is it? Oniiii-chan!?"
Upon being called upon by name, Isshiki happily smiled from ear to ear.
Somehow, when confronted with this kind of result, it's not that bad after all.
"Uh, actually, after all, calling senpai 「Onii-chan」 might be a bit embarrassing."
Bashfully saying so, Isshiki inclined her head slightly upwards.
"… No, calling me in that manner isn't something I told you to do in the first place, is it?"
But, regardless of what I said, it would seem that Isshiki had already resolved herself.
"No! For the sake of becoming senpai's younger sister, I need to at least try that way of addressing senpai! Ah, no, I mean, addressing onii-chan!"
"Haah, it's fine already, just do as you like. So? Is that all I need to be doing?"
"Of course not! The next thing I would like you to do, hmm… please caress my hair!"
"Actually, it just so happens to be the case that, before this I heard something interesting from a certain someone. After a brother and sister fight, at the time of reconciliation, it seems that caressing the younger sibling's hair is the standard, that's why, please! My hair!"
"Isshiki, that kind of thing has definitely come from some kind of anime storyline. In reality, that sort of thing isn't a common occurrence, you know?"
"Eh? But haven't you done that to Komachi-chan's hair before, senpai?"
… Just why would you know that.
Wait. Putting that aside, did she really know Komachi? Have they even met each other?
"Nn? You, have you even met Komachi before?"
"It's not 「you」, it's 「Iroha」!"
"…I-Iroha, did you and Komachi meet at any point?"
"Yep! A while ago, I was out with Yui-senpai and Yukinoshita-senpai, and Komachi-chan had tagged along too! And, at that time, I really hit it off with Komachi-chan! I mean, after all, if you want to take down the commander, you must first shoot their horse, isn't that how the saying goes?"
"Is that so, so you've already met Komachi."
Haah, this might be wishful thinking, but I hope Komachi hasn't been negatively influenced by her already in some way.
"Anyway, please, proceed with caressing my hair."
"Not a chance, that's a skill I can only bring to the surface when face-to-face with Komachi."
"What's with thaaat? Come over here and start as soon as possible, please!"
At which point Isshiki, seated on the opposite side of the desk, began to attack it with loud thumps, simultaneously starting to whine like a spoiled child.
"Muu, looks like after all, I'll have to be the one moving over there, or nothing will ever happen!"
With that said, Isshiki stood up from her chair, carefully navigated around the desk's perimeter and came over to my side.
Then, with a triumphant 「yoisho!」, promptly smoothed out her skirt and sat on my lap.
"…Now what are you doing? Isshiki."
"Like I've been saying, it's 「Iroha」, I-RO-HA."
"Iroha, what are you doing?"
"That's because, if I don't at least do this much, senpai won't be able to do it properly, so… more importantly, my head's here already, so, please proceed."
"No, even so, I can feel the weight."
"Ha!? Just what are you saying here?! Don't you know that girls are as light as feathers?
… Is this much … not possible… after all?"
As she pleaded while looking at me over her shoulder, I could sense moisture starting to form at the corners of her eyes.
Even if you look at me like that, head caressing is one of my Onii-chan skills I've honed specifically for Komachi, but...
Or rather, what's with this person? How could she come over here and sit down on my lap so easily? Just why is it such a simple matter for here to break through my AT field?
Adding on to that, from this fairly close proximity, that sweet smell characteristic of girls was already starting to…
As I reluctantly pondered this peculiar feeling, I started to gently pat her head.
"…fufu. Ah, it's a bit ticklish, senpai."
"Well, that's enough then."
I ceased my movements and lifted my hand.
"Ah- wait! That was way too short!"
But Iroha then firmly grabbed my hand and pressed it back down onto her head.
"…Haah, only for a little while longer, then. Seeing as today's student council work hasn't been fully completed yet."
"Yes yes, I get it!"
After expressing her understanding thus so, she started delightfully humming a tune to herself as she proceeded with some paperwork, while I skimmed my hand back and forth over the surface of her hair.
As this unusual ritual was being carried out –
"Prez, Hikigaya. It's fine already, you can go home."
The vice-president, who had up until this point been in the room working silently throughout, finally gave up and addressed us with a tinge of exasperation.
"Just seeing the two of you like this is tiring me out. Afterwards, I'll finish up the work together with vice-prez, so could both you just leave, please."
Even the usually docile Secretary-chan had some strong words to say on the matter, all the while looking completely limp from exhaustion.
Why do these two look so dead tired? The work isn't THAT troublesome to deal with, is it?
"Ah! Really? Then, we'll be leaving first!"
Iroha, promptly accepting the proposal of Vice-prez and Secretary-chan, immediately jumped off my lap and started making the preparations to go back.
"I'm ready senpai! Let's entrust the rest to them and go!"
"A-ah, seems that way."
With that, Iroha took hold of my hand and quickly led me towards the exit of the room.
Well, those two had been the ones to offer, anyway, so I suppose it's fine?
Then, as we left the student council room together, from the other two who were still seated inside,
" " Haaaahhhhhhh… " "
A heavy, collective sigh could be heard.
And I've come out of hiding again! Just needed a good ol' dose of Iroha fanfic from a certain someone to get things going.
It's been a while since I did this kind of thing. Hopefully this one was satisfactory. I chose this one-shot this time around for its relative simplicity, but as always I've taken the liberty to make adjustments where I thought it would be beneficial.
Well, let me know what you thought. There's a few other decent ones that I've set aside and plan to complete at some point.
I'm targeting to finish off the third chapter of that other thing tomorrow, but we'll see.