Though Summer and Seth started seeing each other and lost their virginity to each other, Summer still wanted their relationship to be secret. Seth refused to put up with this and declared his love for her atop a coffee cart in front of the school. Seth and Summer's relationship became official and continued until Seth's best and pretty much only friend Ryan Atwood announced he'd be returning to his home neighborhood, Chino, after his pregnant ex-girlfriend declared she wanted to keep the baby and raise it in her hometown. Seth tried to make Ryan stay and was distraught at his departure but tried to appear uninterested by it, although it pained him deeply. He couldn't face the idea of becoming a loner once more, and even though he still had Summer, he decided to sail the oceans for the summer in his boat, Summer Breeze, which was named after Summer. He left a note for her, and for his parents, who were distraught over losing both Seth and Ryan in one day.
