We were still at the diner.

But my mind had already reached a new world.
A loud trumpet was sounding, and angels were performing a blessing dance.

Yes, It just came to me!
The fact that she’s my little brother’s girlfriend—That means she is my little sister-in-law!

I looked up at the sky and struck a gut pose.
Then my sister-in-law across from me called out to me in a reluctant tone.

“Umm, umm…Are you okay? Your tears are flowing like those from a manga…”
“Ah, sorry. I’m just a little moved by the fact that humanity has reached a new level. Don’t worry, Aoi, I’m doing just fine.”

“Haa, well, if that’s normal, then I’d be worried, but I’m not going to go through the trouble of…Eh!?”
“Hmm? What’s wrong, Aoi?”
“Name!”

Aoi was trying to drink the tea with a tough face, but halfway through, a look of realization crossed her face and she put down her cup and leaned forward.

“What are you calling me out of the blue? The way you close the distance between us is extreme!”
“That’s fine. You call me Onii-chan too.”
“You call me ‘you(informal)’ in return! You used to call me ‘you(formal)’ the other day!”
“It sure is awkward for both of us to be concerned about our relatives.”
“You’re treating me like one of your own!?”

Aoi’s face twitched.

“I let myself go a little bit and called you Onii-chan for a test, and in a few seconds, this is what I got…I feel like this is messed up. What is it, really?”
“Well, well, calm down, sister-in-law. I’ll get you another cup of tea, okay? One sugar and one milk, right?”
“No need for the excessive spoiling big brother move…I don’t need it. I still have some.”

I smiled refreshingly at Aoi, who was very cautious.
I don’t smile much at girls other than Yuika, but my sister-in-law is special.

“Aoi, I’ve noticed something.”
“To be honest, I don’t really want to hear it…What did you notice?”
“Aoi is Iori’s girlfriend, right? You’re my little brother’s girlfriend, which means you’re my little sister!”

“I don’t want to get caught up in such logic.”
“Eh, you’d rather have a friend from the heart?”
“I said I don’t want to get involved! Did you hear? Did you hear what I said?”

“Calm down, sister-in-law. I’m listening.”
“You just want to call me your sister-in-law…”

“Well, I’ve noticed that the term ‘sister’ isn’t very cute either. That’s why I dared to call you my sister-in-law. You can call me Souta Nii-chan from now on!”

I flashed my teeth and gave a thumbs up.
But for some reason, Aoi was annoyed.

“I’m not going to call you by that after this exchange…”
“Why!?”
“It’s because I caught a glimpse of Souta Nii-chan-san’s perverted nature again, of course.”

“What’s wrong with loving my cute sister-in-law as much as I can?”
“There’s already something crazy out of that line! It’s almost like…”

Aoi averted her gaze and whispered.

“The reasoning behind…the little brother’s girlfriend being the younger sister is not hard to understand, but…sister-in-law is different.”
“Hmm? My sister-in-law is written as, sister, in-law. There’s nothing wrong with that.　I’m not your actual brother, so I prefer to be called brother-in-law. It’s purely a matter of preference.”

“I’m afraid I have a little more respect for you now that you can say perverted requests with a straight face… It’s not that.”

Aoi took a small sip of her tea.
She whispered more, keeping her face hidden by the cup.

“Aside from the sister…you never know if your sister-in-law is really going to be there in the future.”
“What do you mean?”
“This is because…In the future, Souta Nii-chan-san and Onee-chan will be like that, and Iori and I will be like that too…and it will only happen after many stages.”

Aoi turned her head down, probably feeling depressed after saying it to herself.
Her cup was set down without effort, and her bangs hid her expression.

“There is no guarantee that such a happy future awaits you.”
“There is.”
“Heh?”
“It’s right here.”

I slap myself on the chest.
Aoi was apparently very depressed about her future with Iori. As she said, she still lacked confidence.

If that’s the case, then I have to tell her with confidence.
That you’ll be fine.

“I’m going to make Yuika happy. I’m going to put my whole life into making her happy. That’s what I’ve decided.”
“It’s not that easy…”
“It’s that easy. Make up your mind and do it. That’s all you need for a happy ending.”

I said it out loud and smiled confidently on purpose.

“And Iori is my little brother. He’s grown up watching my back. He will do everything in his power to make the woman he loves happy. So don’t worry about it.”

I leaned forward and put my hand on her fluffy hair.

“Ah…”

A small exhale spilled out.
I assured her in a voice clear enough to drown her out.

“If you want a guarantee, Yuika and I are your guarantee for the future. We’ll show you a very happy ending, so follow our backs.”
“…That’s not fair.”

Biting her lip for a moment, Aoi murmured.

Souta Nii-chan-san and Onee-chan are two of Iori’s idols… And the happiness that Souta is trying to achieve is probably in a much harder place than mine…
“Well, she’s a recluse.”

“But if you say it with such confidence…
“Then?”
“It makes me want to work harder…”

Okay, she was starting to cheer up.

“So what Aoi needs to do is to make Iori fall in love with you even more. Don’t worry, Onii-chan will give you the best information.”
“The best information?”
“I know all about Iori’s k*nks.”
“What, you mean…?”

Aoi’s eyes wavered.
It was a priceless piece of information for your girlfriend.

Yes, older and younger brothers have been known to share information closely since ancient times.

There was a time when Iori tried to reveal my k*nks in a letter to Yuika.
In the same way, I can disclose Iori’s k*nks to Aoi!

“Fufufu… You understand now, sister-in-law? Do you understand how great your Onii-chan is?”
“What an annoying smug face…ugh. But I’ll never get a top secret like this from anyone else!”

“Exactly. So you know what to do, right? From now on, you’re going to call me—”
“Mmm~, Souta Onii-chan!”
“Ooh!?”

“I’ll call you that. I’ll sell my soul to the devil if I have to get Iori-kun to turn on properly!　Isn’t this enough? Souta Onii-chan, Souta Onii-chan, Souta Onii-chan!

“Hahahahaha! You’re so cute! Come on, let’s pat you on the head.”
“Tsk…annoying!”

I patted Aoi’s head with a big smile.
Aoi, on the other hand, was treading on the ground, but surprisingly, she doesn’t really hate it. I guess it was true that she was an only child and always wanted a big brother.

The sound of the system echoed in my mind.
Teteren~n!
The Hero Souta has gotten a sister-in-law!

I did it!

And while we were joking around like that, there was a sudden change in the scene.
A third person appeared, who arrived late.
His voice came from the aisle side of the table.

“…What is this hellscape for me?”

The voice sounded dark, like it was coming from the bottom of a well.
Aoi and I were startled, and at the same time turned our attention to the aisle.

It was Kisaragi Iori, 14, in his school uniform.

…Wow, the highlights are gone from his eyes like I’ve never seen before.

And those lightless eyes are staring at my hand as hard as they can.
Well, it’s that hand…that is modestly stroking Aoi’s head all over the place.

“I-Io-Iori…”
“Ah, n-no, Iori-kun. This is not Souta Nii-chan-san’s fault…”

Aoi immediately tried to cover me.
She was a sweet girl after all.
And the fact that she had changed the way she call me to Souta Nii-chan-san was also steady.

…But what about that calmness in this case? I think it would be better to blame it all on me…

A cold sweat ran down my face.
Iori opened his mouth gravely in the air as if gravity had doubled.

“…It’s okay, Aoi-chan. I have a pretty good idea of what happened.”

His mouth was twitching. He was desperately trying to maintain his composure. I’ve never seen Iori like this before.

“I knew this day would come. Souta Nii-chan is very protective of girls, but he’s soft on his family…I thought that if a girl came along who could fill that gap, he would love her like a cat. —But!”

Iori’s eyes widened.
Iori regained the highlight and moved.

He threw out her school bag, flicked my hand, and then, to my surprise, hugged Aoi’s shoulder tightly.

“Don’t get too familiar with her, Souta Nii-chan! Because…”

Iori.
With a red face.
Shouted triumphantly.

 

“—Aoi-chan is my girlfriend!”

 

Zukun!
Aoi and I were both shot through the heart at the same time.

Iori, you, you…!

This was a manly declaration from a normally kind-hearted middle school boy.
I’m going to get a heartbreak shot like this!

I fell down, and Aoi, who was held by him by the shoulders, turned bright red and puffed.
We were all thinking the same thing.

This is good, very good…
This could be used as a strategy to make Iori fall in love with her, and I’ll continue to play the brother and sister-in-law move to make Iori jealous every now and then.

The Onii-chan and sister-in-law looked at each other and nodded deeply in their minds.

“(What do you think, Aoi? The future looks bright, doesn’t it…?”
“(Yes, Souta Onii-chan. I’m very happy right now…)”

I almost collapsed on my seat and turned completely white.
Aoi was still being hugged by Iori, and she was getting all giggly.
When I was half-dead, I hear, “Souta Nii-chan, are you listening to me? Hey!” from Iori.

It was a family restaurant discussion that ended in three different ways.
By the way, the price of two cups of Corkscrew Jumbo Parfait was mind-blowing. As a matter of course, there was no money left for the prepaid card.

Ah God, what should I do about the huge awkwardness explosion problem with Yuika…