A Key

The small backpack clearly wasn't designed to ferry classwork back and forth. It seems more like a day backpack, designed for a girl suffering from a lack of pockets and a disposition against purses. Which is why you only find one thing in the entire backpack. Well, to be more precise one truly intiresting thing and a piece of paper.

Luckily the backpack is light. So light in fact that you even consider making an attempt to sprint after her, but enough time has passed to reduce the viability of that option. Instead you walk briskly back home and take a more in-deph look inside.

The centerpiece of the backpack is a key. It's not a large skeleton key, but more a normal looking one small enough to easily fit on any keychain or keyring. You study it for a moment, but not being a trained locksmith you push it to the side. Next you grab a piece of paper from inside the bag.

It includes her name, Kim Yun-Seung, and a cell phone number. Perhaps she included this in case it got lost, but why she needed an entire backpack for just a single key was baffling. Maybe if you call her, which you would do key or not to be honest, you can find out directly from her. Though, if she wants the key back so bad, it might be a good idea not to let her know you have it just yet.