But when she returns to the school expecting a hero's welcome, only three people show up. Stargirl decides that the best way to become popular is to win the state's public speaking competition, which she does. In response, Leo convinces Stargirl to act more 'normal.' She starts going by her real name (Susan), wears typical teen clothing, and becomes obsessed with being accepted and popular. For a while, he is deliriously happy with their relationship, but as reality sets in, he realizes that the entire school is shunning both of them. They spend more and more time together, and Leo experiences her unusual lifestyle and starts helping her with various projects, such as leaving cards for people they don't know and dropping change on the sidewalk for others to find.

Leo praises Stargirl for her kindness, bravery, and nonconformity, and the two begin a tentative romance. She is shunned by the entire student body, except for her friend Dori Dilson, Leo, and, to some extent, Kevin. Shortly thereafter, Stargirl stops cheering for both teams at games, but cannot stop herself from comforting a hurt player from the opposing team during a playoff basketball game and is blamed for Mica High's loss in the following game. An advising teacher cuts the show short, and it is never aired, but the damage is done. This show's guest is Stargirl, and the session turns into an embarrassing attack on Stargirl's personality and actions. During the show, a 'jury' of students is invited to ask questions of the guest star. Their anger comes to a head during the filming of the student-run television show, Hot Seat, which is run by Leo and his best friend Kevin. Thanks in part to her efforts, the football and cheer season is the best in the school's history, and school spirit flourishes however, students begin to resent Stargirl's habit of cheering for both teams, which before had added to her popularity. However, Stargirl's popularity is short-lived. Her antics on the squad spark a boom in audience attendance at sporting events. Students mimic her behavior, and at lunch, she no longer sits alone. Though at first rejected by most of the students, Stargirl gains a measure of popularity and is asked to join the cheerleading squad after she succeeds in getting the crowd excited about the school's losing football team while cheering for them at a game. When Hillari orders Stargirl not to sing to her on her birthday, Stargirl sings Hillari's name but directs the song to Leo and mentions in front of everyone that she thinks he is cute. One of Stargirl's quirks is singing happy birthday to students when it is their birthday, bringing her ukulele to school to do so. Hillari Kimble, a well known and somewhat popular girl at Leo's school, declares that Stargirl is a fake, and speculation and rumors abound. She is so different that at first, the student body does not know what to make of her. She also brings a ukulele to school every day, as well as her pet rat, Cinnamon. Leo learns that up until this point, she has been homeschooled, but even that doesn't seem to excuse her strange behavior for example, she comes to school in strange outfits-kimono, buckskin, 1920s flapper clothes, and pioneer clothes.

The story picks up two years later with the arrival of Stargirl Caraway at Leo's school, Mica High. After his birthday and collection of porcupine neckties are mentioned in a local newspaper when he's 14, Leo receives a second porcupine necktie, left anonymously. Before the move, his Uncle Pete gives Leo a porcupine necktie as a farewell present, inspiring him to collect more like it. The book begins with a brief introduction to the main character, Leo, at an early age, which is followed by his move from his home state of Pennsylvania to Arizona when he is 12.

Major events in love stargirl