Sam works for the Tops as an event coordinator in the Commons. He's basically a staff member who handles things when they're putting on shows or competitions.
The thing is, Sam used to be a genuine fan of Jack Atlas—he actually looked up to him. But that all went south when Jack gave him the Tuning Magician card as a gift. Sam completely misread the situation and thought Jack was disrespecting him or mocking him somehow. Whatever Jack's actual intention was, Sam took it the wrong way, and that single moment flipped a switch. Now he despises Jack and holds a grudge against the Tops as a whole. It's one of those cases where a misunderstanding spiraled into real animosity.
Content compiled by AnimeList.moe from publicly available sources.
