After that tender moment at Shizuka's place, Kazuki found himself more aware of his feelings for her. He was still adjusting to this new dynamic between them—something subtle had shifted, filling him with an unfamiliar warmth he couldn't shake.
The next day, Shizuka decided to come over to Kazuki's house again to study. This time, though, his little sister, Aoi, was at home. Being the siscon she was, Aoi didn't like the idea of anyone taking Kazuki's attention away, especially not Shizuka.
From the moment Shizuka entered, Aoi hovered nearby, casting suspicious glances at her, eyes narrowed and her lips forming a pout. Kazuki noticed, giving Aoi a soft smile. "Aoi, why don't you go play in your room for a bit? Shizuka and I need to study."
"But why can't I stay?" Aoi protested, her arms crossed tightly. "I want to be with you too, big brother."
Kazuki chuckled, ruffling her hair. "Because we have exams coming up, and it's high school material."
Aoi turned her gaze to Shizuka with a challenging look. Shizuka just laughed, waving playfully. "It's okay, Kazuki. I don't mind if she stays with us for a little bit." She leaned down to Aoi's level, smiling. "How about you help me study? I could use a smart assistant."
Aoi's eyes sparkled at the compliment, but she quickly masked her smile, giving Shizuka a stubborn nod. "Fine… but don't think this means I like you!"
Kazuki smiled in relief, watching as Aoi settled herself on the floor beside Shizuka. Aoi kept up a pout, but soon enough, she began laughing at Shizuka's jokes and listening intently as Shizuka explained a few basics to her.
After a while, Kazuki got up to fetch drinks, leaving Aoi and Shizuka alone. Once Kazuki was out of earshot, Aoi leaned closer, eyeing Shizuka carefully.
"Hey, Shizuka," she began, her voice lowering, "do you… like my brother?"
Shizuka's cheeks flushed a bit, but she kept her composure, smiling kindly. "Yes, Aoi. Your brother is really important to me."
Aoi's expression was a mix of frustration and admiration. "Well… just so you know, I'll always be his number one, okay?"
Shizuka chuckled, reaching out to gently pat Aoi's head. "Of course. You're his little sister, Aoi. No one could ever replace you."
Aoi looked down, trying to hide a small smile, though she still managed to mutter, "Good. Just remember that."
Kazuki returned with drinks and snacks, missing the exchange between the two girls. As he handed out the drinks, he noticed Aoi's softened expression toward Shizuka, feeling a sense of relief.
They spent the rest of the afternoon in a comfortable harmony. Eventually, Aoi wandered off to her room to work on her own homework, leaving Kazuki and Shizuka alone to continue studying. But Kazuki could sense the quiet bond forming between the two girls, and it warmed his heart.
As the sun began to set, Shizuka packed her books and prepared to head home. At the door, she turned to Kazuki, smiling softly.
"Thanks for today, Kazuki," she said. "I think Aoi's starting to warm up to me… maybe."
Kazuki laughed, scratching the back of his neck. "Yeah, she's protective, but she knows when someone's good for me. I think she likes you more than she'll admit."
Shizuka nodded, looking pleased. Then, with a quick glance back to make sure Aoi wasn't watching, she leaned in and gave Kazuki a quick peck on the cheek, her face bright pink.
Kazuki's heart skipped a beat, and he looked at her in shock, his own face growing red. Shizuka just giggled, giving him a playful wave as she stepped out the door.
"See you tomorrow, Kazuki," she said, her eyes sparkling.
Kazuki touched his cheek, feeling her warmth linger. Inside, Aoi peeked out from her room, her cheeks puffed in a pout. She knew Shizuka was important to her brother, but she'd make sure to remind Kazuki just who his favorite girl would always be.