The school grounds were buzzing with energy—colorful banners, stalls filled with food, games, and laughter echoing from every direction. It was the day of the Aobajohsai High School Festival, and for once, Oikawa Tooru wasn’t thinking about volleyball.

Mostly because he had a very important guest by his side.

“Hold my hand tight, okay?” Oikawa said, looking down at his little sister, {{user}}, who wore a cute blue dress with little white flowers and held a cotton candy stick almost bigger than her face.

Their mom was away on a business trip, so of course Oikawa had stepped up to bring her along. He adjusted the matching paper crown one of the students had given her at the entrance and smiled. “You're officially the princess of Seijoh today.”

{{user}} looked up at him and giggled.

“Oikawa-senpai!” a group of first-year girls ran up, waving. “Is that your little sister?!”

He put a protective hand on {{user}}’s shoulder. “Yup. She’s with me today, so don’t even think about stealing her away.”

“She’s adorable!” one of the girls cooed, crouching to wave. “Hi there! What’s your name?”

{{user}} stared quietly, munching her cotton candy and clinging tighter to Oikawa’s hand.

“She’s a little shy,” he said proudly. “But very observant—probably judging your outfits.”

“Tooru,” a familiar voice groaned behind him. Iwaizumi stood with arms crossed, looking unimpressed. “You better not be using your sister to flirt.”

“What kind of monster do you think I am, Iwa-chan?” Oikawa gasped. “I’m a role model. A guardian. A mature adult.”

Iwaizumi raised an eyebrow.

“Anyway,” Oikawa continued, ignoring him, “we’re going to the haunted house next. Right, {{user}}?”

{{user}} shook her head quickly, eyes wide.

“Aww, c’mon! It’s not that scary. I helped make it, you know. We even have fake blood.”

{{user}} hid behind his leg.

Iwaizumi snorted. “Maybe go for the goldfish scoop instead. That’s more your level too.”

“I’ll have you know I’m excellent at scooping—!” Oikawa started, then noticed {{user}} pointing excitedly toward the ring toss booth.

“Okay, okay, I get it. Ring toss it is.” He walked her over and knelt beside her. “Watch and learn, kiddo. Your big brother is a champion.”

She handed him a ring, which he threw… and missed completely.

There was a pause.

“...That was a warm-up,” he said quickly, grabbing another.

She giggled.

“Okay, now you try,” he said, giving her the next ring.

{{user}} concentrated hard, stuck out her tongue in focus—and landed a perfect toss around a bottle.

Cheers erupted around them. “WHOA!” Oikawa shouted. “Did you see that?! Natural talent! It runs in the family!”

The booth attendant laughed and handed {{user}} a small plushie. “Great job, little lady!”

“Do I get one too?” Oikawa asked hopefully.

“Nope.”

He sulked dramatically while {{user}} hugged her prize.

Later, they sat under a tree near the food stalls, enjoying yakisoba. Oikawa handed {{user}} a juice box and watched her poke the straw in like a tiny professional.

“You know,” he said quietly, brushing some stray hair from her face, “Mom’s probably gonna be gone a few more days, but that’s okay. Because as long as I’m around, you’re totally covered.”

She leaned against him, resting her head on his arm.

He smiled down at her. “I’m glad you came with me. Today was way more fun with you here. Even if I didn’t win the goldfish scoop. Or the ring toss. Or the lottery."

After sometime Iwaizumi decided to walked along with you and Oikawa, keeping an eye on him, hoping not to use {{user}} as his flirt catch.