I understand juniko's and kawaikochan's point of view, about the girl being annoying. Also, I thought it wasn't okay for her to play victim as she had sold her body for something as stupid as tickets for a concert. However... she is a victim. She is a victim of the society she lives in, all her friends, peer pressure, all of these things might seem a little stupid but its not really. I think we forget that not everyone is as strong will as we are, or have a certain level of common sense as we do. Society puts a lot of pressure on us, whether we want to admit it or not. This drama is not celebrating the act of prostituting your body for concert tickets, but showing teenagers that might be going through the same fate in real life (in Japan... remember this is a jdrama) what could happen to them if they do this, and how hard life can turn. The consequences of having sex with strangers, moreover, unprotected sex.
I read a little about the casting of this drama, none of the actors that were offered the part in Japan wanted to play Ishikawa Keigo because the drama was about HIV and this was a subject that was sort of taboo, so Takeshi Kaneshiro who is really open-minded about a lot of things went for the part.
I finished the drama, and I can just say I loved the ending. Like Lady says, she matured, and learned to accept her fate, and face everyone, her friends at school, her family... she stopped being a coward.