From: NekoAtsumeGirl

Hide and Seek (숨바꼭질)
By:SeeU

Producer(s)
Ho-ong-i (music, lyrics)
Tyuh (movie)

Theory:

The most accurate one I've thought of/seen is that there were a boy and a girl planning to play the famous horror game in Japan and Korea called "Alone Hide-and-Seek" or "One Man Hide and Seek".I guess you're all pretty familiar of this game wherein a doll would be possessed or even a ghost, it will find you considering the ghost is the "it". But, the boy played with his friend but eventually left her as he ran to a room and locked the poor lady outside leaving her possessed by the spirit, through the pv, it was shown at the beginning that the girl is knocking at the boy's door to let her in until another woman showed (the black haired one) and possessed the girl showing that her eyes changed into a shade of crimson red. After that, it showed the girl trying to find the boy while on the other hand, the boy might have regretted what he did because he was shivering in fear, hiding somewhere. The girl found the boy and the spirit took his body in exchange for winning the game and so he killed the girl starting (*coughs*ending*coughs*)the game again.

WELP! THAT'S ALL! I guess it doesn't really have a secret meaning since it's much more of a story.