From Slightly Sarcastic:

Sugawa Raika is a pretty normal second year in high school... except for her unhealthy obsession with good-looking boys. When she meets Tamaki Jun, a boy at her school, she is just as determined and boy-crazy as she's ever been. But Raika has met her match in Jun; he smiles sweetly at her advances, telling her nicely that he is, in fact, not from planet earth!