That day, I was sitting on the living room sofa and was absentmindedly watching TV.

As I was wasting my day off, I heard Ruka’s voice from across the room.

“Big brother.”

I looked up and saw Ruka standing there; she was already changed into her going-out clothes.

“Do you want to go out now?”

“Where to?”

“A new shopping center just opened in the next town. I heard it’s full of greenery and really pretty, so I thought it would be nice to go see it with you.”

Her eyes were shining with excitement. I had no reason to say no.

“Alright. I’ll get changed.”

“Thank you!”

Seeing Ruka’s happy smile made mine naturally relax, too.

✩ ✩ ✩

Thirty minutes later.

The shopping center, about a five-minute walk from the station, was indeed a beautiful building surrounded by greenery. There were cafes with terrace seating, small shops, and a little observation area.

But the moment I stepped inside, something felt off.

Groups of girls were clinging to boys in ways that didn’t look like normal friends. One group had a single high school boy with four girls around him, and another had five girls surrounding a college-age guy. None of them kept normal personal space; they were sticking way too close. It looked strange.

“Big brother, that café looks lovely.”

Ruka happily looked at the shops and was seemingly unaware of the strange scenes around us.

“Yeah.”

My eyes are drifting around. I felt uneasy.

“Shall we go in?”

“Ah, yeah.”

Ruka led me into the café with terrace seating. After ordering, we sat down, and she happily admired the view.

“It’s so pretty here.”

It really was beautiful, but my attention kept drifting to the other customers. I could feel them glancing at us from time to time.

After our drinks arrived, we sat quietly for a while before Ruka spoke up.

“Big brother.”

“Hm?”

“Did you dislike this kind of place?”

“This kind of place?”

Ruka blushed slightly and spoke in a soft voice.

“…It feels kind of like a date.”

Her words made me pause for a moment.

“I don’t mind.”

“Really?”

Ruka looked a little relieved, but also like something was missing.

We spent the rest of the time chatting lightly, and by evening, we decided to head home.

Near the exit of the shopping center, I heard a familiar laugh.

“Hey, you’re sticking too close to Tomo-kun!”

“Well, I want to stick close, so what can I do?”

“Matsumoto-senpai, do you want to go see a movie with me?”

I turned and saw Matsumoto-senpai walking with four or five girls.

The girls were clearly interested in him, and he stood confidently at the center of the group.

Matsumoto-senpai noticed me and smirked.

“Yo, Saotome. Are you on a date with your little sister?”

Ruka blushed and looked down at his words.

I met Matsumoto-senpai’s gaze calmly and replied evenly.

“…And what if that’s the case?”

“Nah, it’s fine. You guys look like you’re having fun.”

He waved the girls away and said, “I want to talk to a kouhai for a bit, go somewhere else,” and then casually put his arm over my shoulder.

He leaned in and whispered so only I could hear.

“Are you still playing the big brother role? What a waste.”

I didn’t answer. I couldn’t find the words.

“Your younger sister’s really cute. If I were in your place…”

“Stop it.”

I said coldly.

“Oh, did I make you mad? My bad, my bad.”

Matsumoto-senpai shrugged and laughed.

I brushed his arm away and took Ruka’s hand.

“Let’s go, Ruka.”

Ruka looked a little unsure, but let me lead her as we started walking. However, Matsumoto-senpai didn’t give up.

“Don’t get so worked up.”

He followed us with that careless laugh.

Then, he spoke to Ruka boldly right in front of me.

“Hey, little sister. Do you want to go out with me, just the two of us?”

Ruka stepped back in surprise and grabbed my sleeve.

Something inside me snapped.

“…Please stop it.”

My voice was low and filled with restrained anger.

Matsumoto-senpai didn’t lose his teasing smile.

“Why can’t I ask her out?”

He deliberately tried to get closer to her.

I stepped in front of Ruka and glared at him.

“Don’t come near Ruka.”

The moment my gaze hardened, Matsumoto-senpai’s expression flickered with a hint of caution.

But he quickly raised his hands and stepped back.

“Hey, don’t make such a scary face.”

He shrugged with a sly smile.

“Alright, alright, see you later, serious Saotome-kun.”

With that, Matsumoto-senpai went back to the girls.

Ruka and I were left standing there.

I walked toward the exit without saying a word. Ruka followed silently.

On the way to the station, the silence between us felt heavy.

Even on the train, Ruka stared out the window without speaking. Every now and then, she glanced at me, then quickly looked away.

When we reached the station near home and passed through the ticket gates, Ruka finally spoke.

“Big brother.”

“Hm?”

“Can I ask you about that person from earlier?”

She looked thoughtful for a moment, then continued.

“Why did he talk to me?”

“Because you’re cute.”

Ruka’s cheeks flushed, and she looked down shyly.

“B-but he had a lot of girls with him.”

“He’s a womanizer. That guy is.”

Ruka looked up at me with big eyes.

“…Bi brother, if I had gone with him, what would you have done?”

“I don’t even want to think about it.”

Her eyes widened slightly at my answer. Then, she made a small motion as if kicking a stone and murmured quietly.

“I'm sorry for asking something weird. I just… wanted to know.”

I didn’t answer and kept looking ahead, and let out a breath.

I could hear Ruka letting out a small laugh.

“Well, I wouldn’t go out with anyone else anyway.”

We passed through the gates with the sunset shining in, walking home side by side. Ruka slowly moved a little closer, and her shoulder brushed lightly against my arm.

Chapter 11: "I Don't Want My Stepsister to End Up with a Womanizing Senpai!?"