When we were young, most of us had an imaginary friend to play with. And as we grew older, getting so busy trying to grow up and become a successful adult, we slowly forgot about them. It is the same way with Pai, a young doctor, who has returned to Bangkok to continue his studies. However, once he comes back and finds his imaginary best friend, Klong, who also seems to have grown up just like him, waiting for him — he slowly comes to realise that maybe Klong doesn't really want to be a figment of his imagination anymore. For you see, if someone leaves a person who was once the most treasured being in their life — without a goodbye. Wouldn't it grow vengeful and come back to deprive the life of them? It's only fair this way, isn't it? (Source: Soju at MydramaList)