There’s a meaning behind this medley. For those who doesn’t know, I’ll explain:
Everything you see is a mindmap. Each of the 2PM member represents one emotion/theme/whatever you call it.
First, Chansung is longing. He stands outside, wavering the telephone booth, wishing to call the girl and ask her to come back, but at the same time, he knew he had been dumped and thinks if there’s a need to call. That’s why he wavered and sang ‘Again and Again’.
Second, Junho is sadness. The make-up he has showed as if he cried. That’s why he sang ‘I Hate You’, what he wanted wasn’t sadness. That’s why he hated the girl for giving him something not he wanted.
Third, Wooyoung is anger. That’s why he kicked and threw things away. He sang ‘Without You’ due to the anger caused by the girl, that anger allowed him to be optimistic.
Fourth, Junsu is loneliness. He pressed the piano keys, but nothing came out. It portrayed as if the piano is him, the notes are the melodies of his life. But without the girl, his life is quiet, nothing. That’s why when he pressed the keys, nothing came out. He is waiting for the girl to come back and make his life full of melodies again. That’s why he sang ‘Tired of Waiting’.
Fifth, Taecyeon is memory. He dances to reminisce the time he danced with his partner. He sang ‘Only You’ to tell the girl that she’s the only one he loves.
Sixth, Nichkhun is (feel) lost. He walks on the traffic, knowing that he needs to wait for the green light, but doesn’t know that he needs to quickly and cross the road so that he wouldn’t get knocked down. That’s why when the red man flashes again, he stopped, knowing that when the red man appears, we should not cross the road. But he heard cars honking at him, he looked at the vehicles, thinking why isn’t he feeling afraid. This shows that he thinks, without the girl, his life is meaningless. And that, he is not afraid of death. But at the same time, he know he should let go. That’s why he sang ‘Heartbeat’.