Prior to Ryan's arrival he was routinely bullied by the jocks (namely, the water polo players), who would intentionally urinate on his shoes while Marissa, who lived next door since they were in elementary school, did not speak to him until after Ryan's arrival.
He was befriended by Ryan Atwood (Benjamin Mc Kenzie) when the latter was brought home by Sandy.
Before Ryan's arrival, Seth was ignored by most of his peers due to his awkward nature and unusual hobbies.
After finally admitting she liked Seth, Summer grew jealous of Seth's friend Anna Stern (Samaire Armstrong), whom he met at a cotillion dance practice and he shared many interests with, including comics.
They started dating after Seth decided in her favour during a contest for his affection between her and Summer.
However, their relationship was short lived as they broke up when Seth made it obvious that he truly wanted Summer instead and had made the wrong choice.
Anna soon left to go home to Pittsburgh, but she and Seth remained friends.
Besides his awkwardness, his naivety in social norms and relationships contributes to his propensity to draw trouble to himself and not realizing until it's too late, a running gag in the show; for example, he has to be physically stopped by both Zach Stevens and Ryan when he tries to call his crush Alex Kelly even after she hinted for him to stay away because her ex is in town.
He quickly forms a friendship with Ryan as the latter was the first person who befriended him without any preconceived notions and without judging him.
Though Summer and Seth started seeing each other and lost their virginity to each other, Summer still wanted their relationship to be secret.