My Little Sister Suddenly Confessed to Me, but What Am I Supposed to Do by Dating My Little Sister? - Chapter 87 & 88 & 89

Chapter 87: The Title Match Between Two

After that, we strolled along the nearby riverbank until evening and headed home.

My sister was in an incredibly good mood, while I realized I had just put myself in the greatest crisis yet… I made a promise, sure, but then I made another promise on top of it, and now things are seriously dangerous. I said I could barely hold back, but can I actually do it?

You probably don’t know what I’m talking about. There’s no way anyone’s reading this story closely enough to follow…

“We’re home~~”

“Welcome back, Onii-chama, Shiori-neechama!!”

When we opened the front door, Mitsuki was standing there like a guardian deity, waiting for us.

“…How long have you been waiting there?”

My sister asked Mitsuki. Now that she mentioned it, we didn’t send any message saying we were coming back. Meaning she’d been waiting here the whole time…

“I wasn’t waiting that long. I just thought you’d be back soon. Anyway, that doesn’t matter! Shiori-neechama!! It’s time for a showdown!!”

We’re still doing this, huh. I see…

Just as I thought that, Yayoi-san emerged from her study behind Mitsuki and called out to us.

“Ah, Shiori, Yuu. I’ve made good progress on my work, so tomorrow I’ll take you two to Matsumoto to buy your entrance gifts.”

“Eh!!”

At those words, Mitsuki whipped around to look at Yayoi-san.

“Hm? What’s wrong, Mitsuki? Do you want to come too? I wanted to get it ready earlier, but I’ve been so busy. Sorry about that. I thought it’d be nice if you two picked out what you wanted.”

Mitsuki turned back to look at us, tears welling up in her eyes…

“Mitsuki…”

“Anyway, that’s how it is, so don’t make any plans to go out tomorrow, alright?”

With that, Yayoi-san returned to her study.

“Um, then the match will be tomorrow… Actually, if we can’t do it tomorrow, we only have two more days here, and the last day is just going home, so really we only have one day left. So the day after tomorrow, the three of us should…”

“Eh? I thought you were staying for a week, Onii-chama…”

“Ah, I meant ‘this week,’ so it’s really only six days total.”

“Ehhhhhhhhhh?!”

“I mean, even if it’s summer vacation, we can’t stay that long…”

“Nooooo! I don’t want thatttt!”

“Sorry~ We already bought the return Shinkansen tickets, so the day after tomorrow, the three of us will spend the last day together…”

“No!!! I want to be alone with Onii-chamaaa!!! I want to go on a dateee!!”

Mitsuki threw a tantrum in front of me like a spoiled child.

Seeing that, my sister moved from behind me to the front, spreading both arms wide as if to protect me. What is this…?

“I won’t let you. I absolutely won’t lose!!”

Hearing that from my sister, Mitsuki smiled wickedly.

“In other words, tomorrow night is the final battle, Shiori-neechama!!”

“One win, one loss, one draw. Let’s settle this, Mitsuki-chan.”

Wait, this is supposed to be a romcom, right? It feels like a battle scene is about to break out, but we don’t need that.

“Onii-chama! Please choose the game.”

Both of them focused their attention on me. Why do they look so desperate? It’s just a date, right? Just spending a day together, right? Why does it feel like they’re about to fight to the death?

“Uh, don’t make it sound so formal. Let’s see… what’s left? Shogi, Dobutsu Shogi, Go, Gaster? I don’t want censored text for the final match, but I think Dobutsu Shogi is a registered trademark too, so that’s out. That leaves Shogi and Go. To be honest, my only knowledge of Go comes from reading Hikru no Go, so… if I want to enjoy watching, it’d be Shogi. It’s popular these days, too…”

“Then… Shogi it is.”

“Yes!!!”

“Yeah!!!”

Oh, they both seem confident again.

“So you both can play Shogi?”

“Onii-chama, you play Shogi, not ‘hit’ it!!”

“Oh, is that right? But I’m pretty sure when it’s a piece from your hand, you say ‘hit’…”

“Be careful, Onii-chama! If you say something like that on a Nic*nico Shogi livestream, the comment section will be flooded with ‘You play Shogi!’ messages!!”

“I don’t comment or even watch those…”

“By the way, Mitsuki has a rating of 2400 on Shogi Wars!”

“I don’t know what ’24’ or ‘2400’ means, but you sound strong.”

Hearing that, my sister started tapping on her phone.

“I’m fifth-dan on this app.”

She showed me the app on her phone.

It’s the one that says things like “You can do it~~” I have it too. I’m only third-kyu, though… I felt embarrassed by the rank difference, so I played dumb.

“Oh~~ That’s a Shogi app?”

“Eh? It was on your phone, Onii-chan, so I installed it too… You’re third-kyu right now, aren’t you?”

“……………!! H-h-h-how do you knowwwww?! Shiori, you… wh-when did you?! Not just my room, but my phone too?!”

“I know everything about you, Onii-chan. I don’t even need to look at your phone to know. I have that kind of ability!!”

“Ahhhhh! Seriously?! But I have a passcode! How?!”

Ignoring me completely, the two entered further into battle mode… My passcode…

“So our skill levels are about the same, Shiori-neechama.”

“That’s right, Mitsuki-chan. Now it’s a question of who loves Onii-chan more.”

“Mitsuki will absolutely not lose!”

“Me neither!!”

The two shook hands. Seriously, what is this…?

“Where should we play, Mitsuki-chan?”

“I want to concentrate, so either my room or the guest room.”

“Let’s do the guest room. The second floor would be inconvenient in various ways.”

“Yeah, good idea.”

“Then, Onii-chan, please inspect the venue.”

“Huh? Inspect? What’s that?”

“What are you talking about, Onii-chan? It’s standard to inspect the venue the day before a match. This is our Title Match.”

“Wait, a Title Match? You’re not professional players…”

“Onii-chama! The prize is you! In a professional Title Match, it’s just money and honor. Compared to that, this match is worth more than any Title Match!!”

“Eh? Wait, I’m the prize now? I thought it was just spending a day together?”

“I’ll bring the Shogi board and pieces, Shiori-neechama.”

“Got it. I’ll prepare cushions and stuff.”

“Hellooo? Are you listening? Hellooo?”

Ignoring my voice, the two began preparing for tomorrow’s match. Seriously, what is this…?

As the two moved efficiently, a match venue that looked strangely familiar materialized before my stunned eyes. Wait… seriously?

A thick Shogi board like the pros use, beautiful pieces with engravings that looked expensive, proper piece stands, armrests, and even two chess clocks. Why do we even have these?!

“Hon-kaya 5-sun Shogi board with kaya piece stands, boxwood raised pieces, premium armrests, and chess clocks, Shiori-neechama.”

“Yep, perfect. What should we do for time controls?”

“Yayoi-chama probably has work, so I think she’ll come back before evening. We’ll start after she gets back, take a one-hour dinner break, and have two hours each with one-minute increments afterward. How’s that?”

“Yeah! That works. Then it’s a match tomorrow!!”

The two shook hands firmly once more. Do whatever you want…

What about the bath, you ask? We all bathed separately today. And we all slept together in the guest room.

Mitsuki looked puzzled…

Sorry, Mitsuki. We’re hiding just one thing from you…

Chapter 88: The Title Match Between Two

The next morning, the four of us headed to Matsumoto.

On the train, my sister was reading a book of Shogi puzzles, while Mitsuki was devouring a book on the latest opening theories…

When did you even buy that, Shiori?

“What’s with you two? Reading Shogi books all of a sudden.”

Yayoi-san glanced at them and questioned me.

“Who knows?”

I can’t exactly tell her they’re fighting over the rights to me for tomorrow, so I played dumb.

“My husband loved the game, after all. Maybe it’s in the blood?”

She laughed heartily. I suppose that board and set were Grandpa’s mementos…

On a side note, Yayoi-san’s outfit… a simple white shirt and denim jeans, but they’re clearly high-end vintage.

Her shirt is boldly unbuttoned, showing glimpses of what looks like a designer lace bra…

Plus Gucc* sunglasses and a Franck Mullr watch—you know, the luxury one with the curvy numbers.

She’s in her fifties but looks like she’s in her early thirties, or even late twenties.

Her style is incredible and her skin is flawless. No wonder she gets hit on.

Mitsuki is in Gothic Lolita again—isn’t she hot?

My sister is wearing a white off-shoulder dress and a straw hat with a ribbon. Cute as always.

We arrived at Matsumoto Station.

I said I wanted to see Matsumoto Castle, so Yayoi-san told us, “I’ll be at a cafe, you three go ahead.”

We left her and went sightseeing.

“Is this your first time, Mitsuki? Don’t you come here for school trips?”

“Eh? Oh, yeah…” she replied vaguely.

Come to think of it, Mitsuki never talks about school.

She’s been stuck to us the whole summer; doesn’t she play with friends?

Well, I don’t really play with friends either… Wait, I have some. A few…

We crossed several bridges over the moat, and the whole structure came into view.

National Treasure: Matsumoto Castle.

A formidable fortress said to have been built at the end of the Sengoku period to keep watch over Tokugawa Ieyasu.

We decided to go inside, but…

“So steep! These stairs are so steep! This isn’t a staircase, it’s a ladder!”

“Onii-chan, stay behind me! My panties are going to show!”

“If I do that, I’m the one who’ll see them!”

“It’s okay for you to see, just don’t let the people behind us see!”

“I’m not looking! It’s scary! It’s scary climbing without looking up!”

“It’s narrow, Niichama! My clothes are getting caught~~”

“That’s because you’re wearing such a frilly outfit~~”

I never knew castle stairs were this steep.

Everything is low and narrow; people in the past must have been tiny…

No wonder Yayoi-san didn’t come.

We concluded that castles are best viewed from the outside.

Afterward, we shopped at a department store near the station.

Yayoi-san bought me a wallet and Shiori a bag—both decent brand names.

I called her “Granny” to thank her and got kicked for my trouble…

We did some individual shopping and then ate at a French restaurant Yayoi-san frequents.

She ordered by saying, “Just bring some meat and fish and whatever else,” and had them bring whatever wine they recommended.

My grandma is seriously cool.

The reason I’m glossing over the details is that Shiori and Mitsuki were totally checked out.

The conversation didn’t flow.

Yayoi-san was also fidgety, likely worried about her deadline.

Naturally, we headed home right after lunch.

“Now, Niichama, please perform the piece toss.”

As soon as we got back, the two changed and knelt on cushions in the guest room.

They even have folding fans… Did Shiori buy hers at the department store?

The stronger player usually takes the head seat, but since I didn’t know their skill levels, we decided Shiori should sit there because she’s older.

For the piece toss, you throw five “pawn” pieces, right?

I tossed them, relying on my fuzzy knowledge.

“Three promoted pawns. Mitsuki is Black (first move).”

As I announced the result, both of them bowed.

“Please, let’s have a good game.”

They pressed the chess clock.

Mitsuki closed her eyes for a moment to concentrate, then opened her Bishop’s diagonal.

Shiori immediately followed suit.

Mitsuki pushed her Rook’s pawn, and Shiori blocked the diagonal.

“Yagura?”

Mitsuki muttered and advanced her Silver. Shiori did the same.

“Matsumoto Castle, I see.”

Mitsuki grinned and pushed the pawn to 5-f.

Wait, wait, wait. This is a romcom, not The Ryuo’s Wrk is Never Done!*

The “9-year-old loli” overlap is getting way too strong.

On a side note, in the anime, the characters Ai and Ten’ai have the same pronunciation—I wonder how they handled that…

The author must not have been thinking about an anime at all while writing…

The piece development continued, and once both Kings were safely “entrenched” in their Yagura castles, we took a dinner break.

“Is this a funeral…?”

During dinner, the two barely spoke.

They were muttering notations under their breath.

How serious are they? They can even play mental Shogi…

What is with these two geniuses?

The match resumed.

Once they both had less than an hour left on their clocks, the pieces finally clashed.

“2-e Knight!!”

Mitsuki targeted Shiori’s Silver on 3-c.

Shiori advanced her Silver, and Mitsuki immediately took the edge pawn.

“Exchanging a pawn for a Knight?”

Shiori pondered over the unexpected move.

“I have no choice but to take it.”

She took the Knight with her Silver.

Mitsuki pushed her Rook forward, while Shiori went after the Bishop on 4-f.

Mitsuki pulled her Bishop back and pushed her pawn to 8-d.

“1-d Pawn!”

Mitsuki went after the Silver that had just taken the Knight.

Silver takes, Lance takes, Lance takes, then… “8-c Silver!!!”

“A Rook attack!”

“Wrong. This is the target, Shiori-neechama.”

As Mitsuki said this, her Bishop, which had escaped earlier, promoted into a Dragon Horse.

“Ah!”

“Fufu.”

Mitsuki giggled as her Horse and Promoted Silver began eroding the area around Shiori’s King.

“Kh!”

Shiori’s face twisted in agony.

But she fought back, eroding Mitsuki’s right flank with her Lance and pawns.

“You won’t make it in time, Shiori-neechama!!”

Mitsuki used a Gold to fork Shiori’s Rook and Bishop.

It was a situation remarkably similar to chess.

“Never run from a double attack.”

Shiori moved her King to safety.

“The King’s early escape is worth eight moves… but I wonder if you can truly get away?”

Mitsuki took the Rook.

A Gold took back, and Mitsuki dropped her captured Rook at 7-a.

“Unlike chess, I can use the pieces I take, Shiori-neechama.”

“I know that!!”

Even to a third-kyu like me, Mitsuki clearly had the advantage.

But Shiori didn’t give up. She moved her King toward the enemy territory.

Mitsuki took Shiori’s Lance and then her Knight, but Shiori ignored it, pushing her King further.

“Entering the King strategy!!”

As Mitsuki shouted, Shiori grinned.

“I won’t lose! Absolutely!”

Mitsuki snapped open her folding fan.

Indomitable Spirit.

That’s pretty deep for an elementary schooler…

Mitsuki, you haven’t even lived long enough to be “broken” a hundred times yet…

“I won’t lose either.”

Shiori opened her fan and fanned her face.

Onii-chan is My Life!!

…When did you write that?!

Promoting pawns and lances to clear a path, Shiori pushed into the enemy camp to secure her King.

Mitsuki, seemingly unfamiliar with “Entering King” (nyu-gyoku) endgames, began making consecutive mistakes.

She eventually fled her own King into the enemy camp as well.

Both had used up their time and were now in one-minute byoyomi.

Mitsuki entered first but abandoned her allies to do so.

Shiori’s promoted pieces began picking them off.

Both Kings were now settled in the opposite camps, repeatedly dropping and promoting pieces.

Neither could find a checkmate, but neither would stop.

I checked the rules for “Entering King” games on my phone.

The player with fewer than 24 points loses (major pieces are 5 points, minor pieces are 1).

Shiori had lost her Rook earlier but had since captured almost everything else.

I counted the points. Both had over 24.

They both knew it, but they wouldn’t stop. They refused to stop.

If one declared it, it would be a draw (Impasse), or they could apply the amateur 27-point rule.

Either way, it wouldn’t end unless someone spoke up.

With desperate expressions, they moved pieces and slammed the clocks.

They were trembling, perhaps from holding back the need to use the bathroom.

It had been over four hours since dinner.

They were at their limits, yet they wouldn’t quit.

“I won’t lose… I don’t want to lose…” Mitsuki whispered.

“I won’t give Onii-chan up… never…” Shiori muttered.

…I reached out and pulled both of their heads into my chest!

“Eh!”

“Ah!”

A minute of silence followed.

The three of us were still until the chess clock buzzed, signaling the end of time.

“That’s enough! Please, stop…”

I stopped them, my eyes brimming with tears.

“Onii-chan!”

“Onii-chama!”

“Let’s stop, okay? Tomorrow, I’ll make time for Mitsuki and time for Shiori.”

“And we’ll spend the very end together as a three.”

“Onii-chan…”

“Onii-chama…”

They clung to me, and I held them tight.

In the end, the three of us just started wailing.

Seriously, what even is this—?

Chapter 89: The Far Side of the Moon

The moon has a near side and a far side.

The side visible from Earth is the near side, and the opposite is the far side.

People often mistakenly think the moon doesn’t rotate, but it actually does; its rotation period is the same as its orbital period—about 27 days.

Because it rotates once for every revolution around Earth, the moon always shows us the same face.

The near side features famous plains called “seas” that look like rabbits or crabs, but the far side has almost none.

The far side consists only of rugged, jagged craters.

The beautiful moon we see hides a completely different expression on its back—one never seen from Earth, as if it possesses a will to never show its true self.

“Niichama~~”

I’m currently spending some one-on-one time with Mitsuki in her room.

Since the match ended in a draw—though Mitsuki technically won by points—Shiori offered to let us go out for the day while she packed.

However, Mitsuki stubbornly refused, insisting that since it was a draw, she only needed the morning.

With only half a day, there wasn’t time to go anywhere, so we’re just talking in her room.

And that leads to the current situation…

“Niichama~~”

“Um, Mitsuki-san, why are you sitting on my lap instead of across from me?”

“Ehh? Because I want to~~ And because you’re the prize~~”

“It feels like you’re the prize now…”

“Ehh? Really? Then please take Mitsuki as your prize~~”

“No, no, no, no.”

“Ehhh? You don’t want me~~?”

“An elementary schooler as a ‘prize’ is way past a ban; that’s the kind of trouble I can’t come back from. I’m not ‘taking’ you.”

Still, with her long hair, she looks like a Japanese doll you’d want to display and protect.

“Were you really okay not going out somewhere?”

“Yeah. I just wanted to talk quietly with you, Niichama. Just us.”

“If that’s all you wanted, you didn’t have to fight Shiori. She would have understood if you just asked…”

“No. Aside from being with you, I wanted to properly challenge Shiori-neechama. She really is amazing, though…”

“A fourth grader drawing against a high schooler in a mental game makes you the amazing one, Mitsuki.”

“No. I couldn’t even win at my best game. In anything else, I would have lost completely.”

“Why do you feel so strongly about not losing to Shiori?”

“……Because Shiori-neechama is my goal, my rival, and someone worthy of my respect.”

“I see… but you don’t need to push yourself so hard yet. You read this massive amount of books every day—aren’t you overdoing it?”

“I think you should play more. You’ve been with us the whole time, but what about your school friends? Are they okay with you being gone?”

“………..”

“Hm? What’s wrong?”

“Niichama… are friends… necessary?”

“Eh?”

“I read it in a book once—the probability of staying friends with schoolmates throughout your life.”

“How many people do you think still socialize with school friends after becoming adults and starting families? Only a few, if any. Many have zero. Do you think there’s a point in forcing shallow relationships right now?”

“Well, uh… but playing with friends is fun…”

My words have zero persuasive power coming from me. But this doesn’t sound like a fourth grader; she sounds like someone who has reached a state of detached resignation.

“Not at all. They say ‘I don’t get it’ or ‘I can’t do it’ over the smallest things. And when I show them, they just say it’s because I’m a ‘genius’.”

“What do they know about being a genius? I put in the effort! They don’t even know what a real genius looks like!!”

“A real genius? Do you know one?”

“…Shiori-neechama and Yayoi-san.”

“Ah…”

Certainly, those two might be geniuses, but from my perspective, Mitsuki has incredible talent as well.

“Those two are my goals. I want to catch up to Shiori-neechama. I want to beat her.”

“I see. That’s a tough goal.”

“Yeah. That’s why I don’t have time to waste playing with friends.”

“Then you shouldn’t be with someone like me; you should be with Shiori.”

At those words, Mitsuki looked up from my lap and smiled.

“No. Because you are the greatest genius of all, Niichama. I have to be with you and absorb as much as I can~~”

“Huh? Me, a genius?”

What is this kid talking about? Me, the personification of “average”?

“Yeah. Shiori-neechama and Yayoi-san are goals. But you, Niichama… you aren’t a goal. You’re the kind of genius I’ll never be able to match as long as I live…”

“You and Shiori both overestimate me. I have no talent or charm. I’m just ordinary.”

Seriously, give me a break. I know myself best, and there’s nothing special there.

“Hmm. Shiori-neechama said you were charming, though.”

“Eh? Ah, well…”

“I see. Your charm, huh? So that’s how Shiori-neechama feels.”

“What? Huh?”

“Ehehe. I see, so that’s how it is for her~~”

“What are you talking about?”

“Now, I wonder what it could be~~ Mitsuki doesn’t know~~”

“You just mocked your friends for saying ‘I don’t know’…”

Still, having no friends… it worries me. Especially in a rural area like this, she must feel so isolated because her mind is so advanced. Her peers must look like toddlers to her. It’s the classic suffering of a genius.

“But, we’re going home tomorrow. Won’t you be lonely without any friends?”

At that, Mitsuki spun around on my lap, hugged me, and buried her face in my chest.

“Wait! Mitsuki!”

“…………I’ll be lonely… I am lonely… I don’t need friends, but… I’ll be so lonely if you and Shiori-neechama leave…”

“Don’t go… Don’t go home… Ugh… Wahhhhhhhhhh!”

“Mitsuki…”

I stroked her long, beautiful hair.

“Ugh… I endured it last year… I thought I shouldn’t disturb you because of your exams… but I was so lonely… I wanted to see you. Is it over already? Stay longer, stay by Mitsuki’s side, don’t leave meeeee…”

She squeezed me with all her strength, as if desperate to never let go.

“Mitsuki… I’ll come back. I’ll come back for the New Year. I have to come get New Year’s money from Yayoi-san anyway.”

I gently held her head. Her hair smelled sweet… No, I’m not a lolicon. I’m not…

“Yeah…”

“Ah! I know. You should come to our house next time. You’re old enough to ride the Shinkansen by yourself now, aren’t you?”

“Eh? Can I… really come? Niichama…”

Mitsuki looked up at me. Crap, she’s actually cute… Wait, am I a bit of a lolicon? No, no, no.

“Of course. Mom wanted to see you too. Come whenever you feel lonely.”

“Yeah!!!! I love you, Niichamaaaaa!!!”

“Uwahhhhh!”

The fact that Mitsuki kissed me on the cheek—please keep that strictly between us. Especially, for the love of god, keep it a secret from my sister…