The show began with seven main characters which eventually became 9 by the end of the first season. Since then, characters from that first season have left the show, with new main characters having been both written in and out of the series. Originally, it follows the life of Ryan Atwood, a troubled but tough young man from a broken home who is adopted by the wealthy and philanthropic Sandy and Kirsten Cohen. Ryan and his surrogate brother Seth, a socially awkward yet quick-witted teenager, deal with life as outsiders in the high-class world of Newport Beach. Ryan and Seth spend much time navigating their relationships with girl-next-door Marissa Cooper and Seth's childhood crush Summer Roberts.