Kim Yewon has a set of list - things she wanted to do before she finishes high school. One of the things she hasn't cross out yet is the scavenger hunt. Next to 'having a boyfriend' which is (sadly) not going to happen any sooner. 

She heard it from the seniors. They said that the game is like the final chapter of high school experience. 

Usually this kind of thing is more of a Hwang Eunbi type of activity. But thanks to her non stop blabbering, the idea of playing it eventually got stuck in her head. 

She knew that almost everyone is going to be there. Including Chanwoo aka her secret crush. Her bff, Eunbi and her platonic bff, Moonbin. The one who likes to hype things - Seungkwan and the one who always get hyped - Pinky. The person-she-wished-to-be-close-friends-with, Dahyun and the person-she-wished-to-just-stay-as-acquaintance, Vernon. Seems like the whole class will be there. 

As well as a group of seniors as the organisers/judges. A rumor has it that Red Velvet Irene is also going to come (since she used to go to this school). 

In just one day so many things could happen. Memories will be made. Hearts will be broken. Secrets will be revealed. Those typical teenager stuffs. 

But,

What if the memory that you want to keep forever becomes the memory that you want to forget forever?