The reason I live is you
I don’t think I can see you anymore, I think I’m really dying
The person to love me is you
Shine on me in the darkness
You’re like an angel, who has left me and gone somewhere
I need you
But this song definitely grew on me the more I listened to it. If you, reader, do not like this song at first, then I hope you'll take my advice. Put the song away for a while, then come back to it. Listen to it a few more times. You may want to search out the English subtitles, because they definitely clarified the video for me.
The lyrics of this song describe an angel-like girl. You'll notice they sing, "cheonsa gateun neo" just before the chorus, which means "You're like an angel". This girl has disappeared, and because of this, the man is losing his mind missing her so much.
So I miss you (I think of you) and I need you (every day)
My wasted self is so pitiful
Hug me (I don’t have anyone) Embrace me (but you)
You’re like an angel