Initial storyline idea

I thought that it would be a good idea to have a boy who is in love with a girl from his school but he has never told her. So the story begins with a voice over of him descirbing her. Then, we hear the girl talking about a boy and how much she loves him but she is writing it in her diary.
The effect I want to create is that the audience will believe that they are in love with each other but they daren't say it to one another. However, at the end of the film I want them both to be stood opposite eachother on different sides of a trainline. We will hear the boy (using a voice over) that he is going to tell her his feelings. However, as the train stops at the station the girls boyfreind will get off and the audience will realise that she was describing her boyfriend instead of the boy they have been led to believe.