The Case Where I Found Out My Big Sister with a Brother Complex Was Actually My Stepsister, Tried to Hide It, but She Found Out Immediately and Became Uncontrollable - 34

Chapter 34: Nee-san’s Birthday

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“Happy birthday, Nee-san!”

“Tsumugu~! Thank you~!”

Today was November 9th, the long-awaited birthday of my big sister. This morning’s breakfast was a classic whole cake with strawberries on top of whipped cream, which we had gone to buy together the day before. And now, with my big sister blowing out the candles on that cake, we were celebrating her birthday.

“Really, I think the reason I’ve been able to enjoy these past 18 years so much is all thanks to you, Tsumugu! Thank you so much!”

“I should be the one thanking you, Nee-san. You’ve been looking after me ever since I was born. I’m really grateful to you.”

We expressed our gratitude to each other and then shared the cake. The cake was delicious, sweet, and it made my big sister’s birthday even more special. After the two of us finished the whole cake, my big sister said to me.

“You’re going out with me today, right?”

Yes, since it was her birthday today, we had talked about going out together for the first time in a while, but—

“Yeah, but before that, there’s something I want you to have, Nee-san.”

Saying that, I handed my big sister the birthday present I had prepared—a sparkling expensive pendant with jewel-like detail.

“Eh…!? What is this beautiful pendant!?”

“It’s your birthday present, Nee-san. I think something this pretty suits you best.”

Smiling, my big sister accepted it and fastened it around her neck.

“Does it look good on me?”

“Yeah, it looks great.”

“In that case, I’m going to wear this pendant you gave me and go out with you today! I really love it!”

“I’m glad you feel that way.”

And so, today, I went out with my big sister, who was wearing the pendant I had given her around her neck. The first place we visited together was a clothing store. At my big sister’s suggestion, I tried on various outfits, and I also picked out clothes I thought would look good on her for her to try on.

“Just as I expected, Tsumugu looks good in anything you wear~! But I guess it’s because you yourself are cool, not the clothes!”

“If you’re going to say that, I think it’s more true for you, Nee-san. You look beautiful in anything, and even in cute-style clothes, you look adorable. Everything suits you.”

As siblings, we complimented each other. Next, since we wanted a place to relax, we went to a café together.

“When we came to a café together back when you had just started high school, you couldn’t drink black coffee. I wonder if you can now?”

My big sister had always preferred black coffee, and I used to try to imitate her, but I just couldn’t handle the bitterness… But now that I had become a second-year high school student, there was no way I would admit that I still couldn’t drink black coffee.

“I-I can drink it now.”

Trying to act cool, I answered that way, but my big sister smiled and said to the server.

“One black coffee and one milk tea, please.”

…Huh? I’ve never seen my big sister order milk tea before… Maybe she’s just in a different mood today because it’s her birthday?

“Understood!”

The server cheerfully responded and told us to wait near the edge of the register… Just in case, I asked my big sister.

“Nee-san, the milk tea is…?”

“You had ‘I still can’t drink black coffee’ written all over your face, Tsumugu.”

“Nee-san…!”

She was completely right, and realizing she had seen right through me made me feel a bit embarrassed… After that, we chatted leisurely at the café and browsed for some tasty food together. Before we knew it, the sun had started to set, and we headed home.

“Today was so much fun~!”

“Yeah, it really was.”

As we shared our impressions of the day when the mood around my big sister suddenly changed.

“Tsumugu… Do you remember when I said I’d tell you something I’ve been hiding on my birthday?”

“I remember.”

“…Well, starting now─”

Just as she began to say something, my phone rang. I apologized to my big sister, took the phone from my pocket, and checked the caller.

“…It’s Mom.”

“Mom…? She called me early this morning to wish me a happy birthday and everything, but I wonder what she wants with you?”

My big sister didn’t seem to have any idea, but I did. It was something important—something that would affect her future… As soon as the call ended, I told her.

“…I don’t know, but since she’s calling me, I’m sure it doesn’t concern you. I’ll call her back real quick.”

“Okay, take your time.”

I told a small lie to my big sister before going upstairs and called Mom back. My mother asked me if I was getting along with my big sister, and of course, I told her we were. Then the next thing she said was…

“…There it is.”

The second drawer in Mom’s desk, all the way in the back. She said I could decide what to do after seeing what was there, and then hung up… Following her instructions, I reached into the far back of the second drawer and took out the letter.

I read it.

『You can decide for yourself whether to tell Nozomi about this or not. After all, you’re the one closest to her right now, Tsumugu. Actually──』

And then the next line froze me in place.

『Tsumugu and Nozomi are not blood-related. You two are step-siblings.』

“…What?”

My mind went blank. My brain froze. There was no blood relation between me and Nee-san?

This wasn’t something you’d joke about… So what the heck—

“Tsumugu~? Why are you in Mom’s room?”

Nee-san…! This was bad. I hadn’t processed it myself yet, but at the very least, I knew that I couldn’t let her see this letter yet. I quickly hid it behind my back.

“N-Nee-san, um, Mom asked me over the phone to do some cleaning. You know, since she’s overseas and she’s worried the room isn’t getting cleaned properly.”

I tried to cover it up with poorly made excuses. My big sister stepped closer and said.

“Tsumugu… You lied to me earlier, didn’t you? You said Mom’s call wasn’t about me… But I’ve been with you long enough to know when you’re lying. Why did you lie?”

“That’s because…”

“Are you hiding something behind your back?”

“…!”

As I tried to keep her from taking it, before I even realized, the letter was already in her hands.

“N-Nee-san, if you read that──”

But… She had already read it. She let the letter fall to the floor. My big sister and I shared a deep bond, one deeper than blood ever could be. Despite that, when I thought about how much my big sister had done for me as a sister until now….

“Eh!? …Tsumugu, based on what’s written here… Does that mean…  We can get married!?”

Contrary to what I had expected, my big sister looked brighter than ever, as if she had just found the one light in the world, and said that with a beaming smile.

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