The first season of Netflix's 13 Reasons Why reveals the unfortunate series of events leading up to and following the suicide of high school teenager Hannah Baker. Following her death, the students of Liberty High are introduced to a series of tapes Hannah records to explain the events that lead her to her to end her life.
One student, Clay Jensen, who had been particularly fond of Hannah, takes a special interest in the tapes. Unlike his peers, however, Clay doesn't actually do any harm to Hannah. Instead, Hannah chooses to include him in the tapes because she feels he needs to hear her side of the story.
Clay is a supportive friend to Hannah, often being a sounding board for her to vent to during their shifts together working at the local movie theatre. Though he momentarily feels guilty for his near-sexual interaction with Hannah at Jessica Davis's house party, Hannah holds no anger toward him. The event is a trigger for her, following her encounters with other boys at their school.
Clay struggles with the idea that he hadn't been there for Hannah enough, but as the show progresses, we see Clay spearhead the hunt to hold Bryce Walker accountable for his actions. Clay even goes as far as taking a beating from Bryce to tape his confession of raping Hannah.
Clay isn't guilty of doing anything to Hannah, he only feels guilt because of his lack of action — but there's no way he could have known how much pain she had been in.