Thank you to ExoticDreams for the tips! Below is a more detailed and (hopefully) improved version of the previous oneshot.

He hid his smile behind a mug of coffee, his eyes crinkling in delight.

His gaze trailed her every move. The subtle flip of her hair – her twinkling wide eyes – her smile. And oh, how he longed to hear her laugh again.

It had become a daily ritual for him now, to watch her like this. Each time, he ached to hug her, kiss her, love her – but that, he knew, would only cause her trouble. After all, she was his noona. He was her dongsaeng. They were even working for the same company. Yoochun thought that they probably just weren’t meant to be.

But it's not like he wanted to love her. He just couldn’t help it.

Then - hahaha! - there it was. A sound loud and light, rippling through the room.

Yoochun spun around in his seat. As he watched her eyes widening, her hands flying to as she doubled up in laughter, his smile grew.

She'd once told him that she hated her laugh. She thought it was unladylike. Loud. At the time, Yoochun thought nothing of it.

But then he'd seen her smile. He'd seen her shoulders heaving, tears streaming down her cheeks. Seen her grieving, seen her hurt. Falling in love with her, he realised, had been a gradual process.

And now, every time she giggled, snorting so adorably, he felt his heart melt like butter on toast.

Unknowingly, she did that to him a lot. She was just like that. Infectious. Bright.

Yoochun sank back into his seat and slurped his coffee in content. Perhaps this was just a lingering crush. It would wear off after awhile, he was sure. But for now, he would just have to stick with--

 “Yoochun-ah!”

Yoochun looked up, abruptly.

Song Jihyo, the love of his life. “Ah… noona. Annyeong.”

Jihyo smiled. “Annyeong,” she said, looking over her shoulder. “The C-JeS Family’s going out for a drink tonight.” She grabbed his hand and helped him up. “Come on! Let’s get going.”

Yoochun reddened – and as he let himself be dragged along, he quietly decided that this particular crush was here to stay.