[1] The drama starts with Han Tae-woong (Hyun Bin), a quiet, 17-year-old math genius, entering a prestigious high school.

In a highly anticipated International Math Olympiad, Jung-kyu fails to fulfill his father's expectations to win the gold medal, and commits suicide in shame.

Tae-woong, who wins the gold medal instead, struggles from guilt, as he feels like he is partly responsible for Jung-kyu's death.

He abandoned his mother, dropped out of school, left mathematics, and pursued boxing in honor of Jung-kyu, but he still bears painful memories of his past.

They end up falling in love, but Tae-woong discovers that she was the little girl that he met eight years earlier, and that she is Jung-kyu's little sister.