Sakino is a tomboy who loves to play soccer. One day during practice she yells at a boy named Kazuki Aihara about him being halfhearted.

Spoiler

He soon realizes that yes, he was being halfhearted and starts to become an excellent defender during the games, which really makes Sakino start to love him. But after getting his head into the game, he becomes interested in another girl, Eriko Futami, which makes him start to become distracted. After Sakino finds out that Futami and Kazuki were doing experiments to see why people fall in love, Sakino yells at Futami and makes her quit the experiments, but as a result, Kazuki starts to drift away from soccer. She sets up a time with Kazuki to meet at a park and also invited Futami so they both can talk things through. Her planned failed. Later on, Kazuki tries to reach out to Futami by practicing romantic lines in front of her apartment door with her watching through the video receiver. Which makes them both realize, that they are both in love with each other. One morning Sakino sees Futami and Kazuki walking to school together and then realizes that she made a big mistake by making the two of them get together again. She lost the boy that she fell in love with.