It's been years since Kim Jongin, Kai, searching his childhood friend.He search everywhere but there's no luck.Though, he still keep searching for that friend because he still remember promise with his friend.The promise that he never failed to keep it...

However that promise vanish like air when Kai saw a text on his phone.

It says,'Kai, give up on searching me.Don't look for me.I'm fine but you should stop before it's too late.Don't ask how I got your number and where am I because I won't stay by your side.Oh, and the promise we made,just forget about it.I know you still remember it but I would like you to just throw that promise from you and live your life without me.I hope you will move on and live a happy life...Goodbye, Kai'

And there Kai, who always cheerful, never give up on doing something and also that always good on controlling his emotions is now burst into tears.He never thought or even imagine that his childhood friend leave him like this when he give all his best to look for the person and yet the person just leave him without seeing him in person.He is still in tears but for a while, his mind is now in ease.He then thought,"No...she must not leave me.She should say this in person not in text.So I cannot accept this.She should also need to give me a good reason why is she leaving me.Sorry, but I will not give up even if it cost my life and also the promise we made.I will never throw it." 

After encouraging himself he went out with confidence.When his phone is at his house, an unread message came.It says,'You are very hard-headed.Although you've just cried just now, you just have to encourage yourself to look for me but I'll tell you again, give up now."

So can Kai found his friend? Why would the person told Kai to give up, does she had a reason to do this? And how did she knew that Kai was crying?

Also what promise did she and Kai made?  The answers will be in this story.