Seth Massey

Seth is a minor antagonist in the 2017 Netflix Original 13 Reasons Why. He is the abusive boyfriend of Justin Foley's mother.

He is portrayed by Matthew Alan.

Biography
Seth is first seen in Justin's apartment in season 1. Jessica, Justin's girlfriend, goes to the Foleys' apartment to look for Justin. Seth goes up to Jessica and rudely tells her that Justin's mother is worried sick about him. He is later seen again with Justin's mother while putting his feet on the table. Justin angrily tells Seth to put his feet of the table, and Seth tells him not to f*** with him. In the penultimate episode of season 1, Seth becomes angry and annoyed with the cops stopping by his apartment and handing him subpoenas. He angrily blames Justin, and when Justin yells at him, Seth slams him onto the wall and starts choking him. Before he could strangle Justin to death, Justin's mother stops him, and Seth tells him to go live with that rich buddy of his. This drove Justin to run away from home and become homeless. In season 2, Mr. Porter, the school guidance counselor, stops by the Foleys' apartment. Seth goes up to him, aggressively tells him that Justin stole money from him, and starts a fight with him. The police breaks the two up and takes them to the police station. In the final episode, while everyone is at the Monet's coffee shop honoring Hannah, Seth angrily stares at Justin in his car while Justin is talking to Clay.

Personality
Seth is a very violent and aggressive drug dealer. He is shown strangling Justin onscreen, and could have killed him if Justin's mother didn't stop him. He also starts a fight with Mr. Porter, and ended up with both of them getting dragged to the police station.