Hateshinai tameiki (1999)

Kawase is a high school student going through the kind of stresses that most high school students go through. One day, he meets Reiko, a girl he used to know when they were much younger, who is now going to another school. They talk for a while, and Kawase soon finds himself infatuated with her. Things are looking up for him until he sees her at the train station, accepting money from a businessman and giving him a hug as they part. Could she really be doing what Kawase thinks she's doing?