Easy!
The guy on top is sad because his hot Asian girlfriend is texting the douchebag on the subway!
The subway guy is a player, she thinks he is the bad boy she needs, but in fact, she is just one of the several girls he is currently texting with.
After they hook up, he will start ignoring her texts because she will become all clingy and he will move onto the next girl.
Realizing her mistake, she will try get back to together with the first guy, realizing he was in fact, the better choice.
However, he will have since moved on to another hot Asian chick, so she screwed herself up by leaving him in the first place!