Jump Start!

Seventeen-year-old Izzy Daniels (Corbin Bleu) is a star boxer and the son of a golden-glove champion. His eight year old sister, Karin, is crazy about Double Dutch and Izzy is asked to take Karin and her friends to a Double Dutch competition, where Mary and her team are entering. Izzy has often seen them Double Dutch and is always bothering them, but during the competition he acts out of character, standing and cheering along with everyone else.Izzy finds he has a crush on his friend and neighbor Mary (Keke Palmer), a member of the jump team The Joy Jumpers, who place fourth in the tournament. They make the city finals, but when Yolanda, the fourth member of the team, decides to quit and join their rival team, The Dutch Dragons, they face the prospect of forfeiting the tournament. Izzy, after learning of Yolanda's departure, quips "Why, did she finally figure out Double Dutch is lame?" Mary then challenges Izzy to speed jump, and when he does it much better than they expect, they ask him to join the team, but he refuses because of what his friends might think. When the other members of the Joy Jumpers, Keisha and Shauna, ask him to fill in until they find a permanent replacement, he finally relents. His conditions are that they practice before school and in his dad's boxing gym, where no one's going to watch. Mary also has a crush on him.Meanwhile, Izzy has a boxing match with Rodney Tyler, the school bully, determining who will win the "Golden Gloves", which goes to the best boxer. Izzy beats him, but Rodney doesn't accept it. He claims he just got lucky and pushes Izzy for a rematch. Izzy says no, and walks out of the gym.Izzy improves tremendously at Double Dutch, and begins to love the sport. He tells the Joy Jumpers that he'd like to be on their team permanently, and they happily agree. Izzy and Mary starts to fall in love with each other and share a romantic moment and a kiss on their fire-escape. However, when Rodney finds Izzy jumping Double Dutch before class, he snaps some photos, prints them and hangs them all over the school. He then tells Izzy, "So that's why you won't give me a rematch! 'Cuz you're too busy jumping Double Dutch!" Izzy becomes mad and says he'll do the rematch. But in the middle of the fight, he tells Rodney that he's sick of being mad and that he's not going to let his anger control him. He walks out of the match and Rodney runs after him, intent on beating him up. But he trips on the cords surrounding the ring, giving Izzy a chance to get even. Instead, he just walks out. Mary tries to convince him not to quit their team but Izzy coldly ignores her and wants nothing more to do with her and the team. Mary is disappointed in him and she leaves.The only girl boxer, Tammy, understands how Izzy feels. She gives him a pep talk on how she never quit boxing when the guys teased her, and that he shouldn't quit either, just because they made fun of him.Meanwhile, Mary, Keisha and Shauna meet up for the city finals, but without Izzy, they feel like giving up. Izzy then walks in and asks, "What, were you really gonna start without me?" He apologizes and Mary smiles and hands him a uniform. They change their name to the Hot Chili Steppers and all is forgiven as the tournament begins. They get first in the compulsory, then second in speed. This ties them with the Dutch Dragons and the freestyle will determine it all. The Hot Chili Steppers get first, and go on to the State Championship.After their performance, Izzy notices Rodney in the crowd, and asks him for a truce, which he accepts. Izzy had finally won the respect of his dad Kenneth (David Reivers) and Mary's love.The narrator in the story was Rodney, and he was telling the story to kids, so the movie was depicted to be a story which Rodney was telling, he also states to one of the kids that Izzy and Mary are now a couple. The film closes with Izzy teaching his dad to jump rope with the help of his little sister, Mary and the other girls.

Question: Who is Izzy's sister?
Answer: Karin