Every Wednesday, Noh Yunah finds a letter waiting in her locker that is anonymous, thoughtful, and written with a familiarity that lingers. She never asks who it's from. Park Minju lives quietly on the edges of the same school, keeping her world small and controlled. Writing is the only place where she allows herself to be honest. As senior year unfolds, routines begin to shift, and what has remained unsaid for years starts to press gently but persistently toward the surface.

In high school, Haerin was the quiet, eccentric girl who felt out of place among her peers. She found solace in her small group of friends, but Danielle, always the popular, charming student, seemed like she lived in an entirely different world. Yet, the two shared an unspoken connection, with Danielle treating Haerin with a kindness that made her feel seen. Despite their differences, their bond deepened until that same bond caused them to drift apart. Years later, Haerin had transformed into an attractive veterinarian, no longer the shy, awkward girl from high school. Unexpectedly, Danielle walked into her clinic, effortlessly poised and radiant as ever. The brief moment they shared in high school suddenly felt alive again, bringing back memories Haerin had buried long ago. Would they be able to pick up where they left off, or had too much time passed?

Minju is top of her class, quiet, focused, and allergic to school drama. Noh Yunah is everything she can't stand: popular, loud, reckless... and rumoured to leave a different girl heartbroken every week. When Minju is forced to be Yunah's lab partner, she expects the worst. But behind Yunah's smirk and reputation is someone unexpectedly thoughtful and deeply insecure. The more time they spend together, the more Minju starts to question what she thought she knew about Yunah. And Yunah? She's already fallen. She just doesn't believe someone like Minju could ever feel the same.