Ever since they were children, being the older one, Yujin is Wonyoung's guardian. 

They grew up with the older protecting the younger from other people, boys who dared to date her, or those girls sending hate and spreading nonsense out of pure jealousy. 

Yujin is always there. As the best friend since diaper days, she always guides her best friend to almost anything. From studies, to sports, to just simply talk about their own lives. 

Until the day of the accident. Everything happened so fast, and the next thing Wonyoung knew, Yujin took the hit to protect her. 

Yujin lost her eyesight afterwards. Wonyoung cried, blaming herself because of what happened to one of the most important people in her life. 

"I'm sorry." Wonyoung whispered, still sobbing. 

"Don't be." She said. "It was never your fault Wonyoungie." Yujin still managed to smile despite being hurt deep inside. It was never Wonyoung's fault. And never will be.

Yujin was Wonyoung's guardian. Now it's her turn to to be there and guide Yujin. 

 Perhaps they are each other's guardian after all. And no one can change that.