Cassette 5A

In Cassette 5A the reader gets to know why Clay is on the tapes.
Clay Jensen an Hannah Baker meet at a party where they do a long conversation about anything and everything. Later Clay kisses Hannah, but she pushes him away and run away.
Hannah explains in the tapes that Clay is not a reason for her suicide. He is on the list, because Hannah wants to explain him the situation. She stops kissing him, because she remembers that everytime she starts to trust a person, the person hurts her. She made this tape to apologize him.

Courtney Crimsen

Hey, guys.
I want to tell you something about Courtney and what she has done to upset Hannah.

Courtney is the fifth person on Hannah's list.
Courtney Crimsen is known as a perfect girl. She is beautiful, helpful and nice to everyone.
She helps Hannah when she finds out that someone takes picture from her in her own house.
Courtney is very nice to Hannah and they spend a lot of time together, so Hannah really thinks they become friends, but Courtney is just another person who disappoints her. She just wants to aufpolieren her image.
One day, Hannah and Courtney go to a party. At this party she tells everybody that Hannah has a lot of sex toys. Courtney is very egoistic. She wants everybody to like her and she does not care if she hurts the feelings of other persons. All that she cares about is her own image.

I can understand why Hannah feels hurt by Courtney. It's hard when someone spread rumors about you but it is harder get disappointed by a person you like.