They say  two moments are the happiest in a human's life : The day he's born and the day he figures out why.

 Welcome to Kim Taeyeon's dull life, an average girl who gets by without getting noticed,having an "oh-so-perfect" twin sister didn't make it any better.Taeyeon was quite aware that all she did in her miserable life was existing, until she meets someone that will make her see the world from another perspective, she will learn then that existing isn't as pathetic as people think but it was an art indeed.