Olivia is a "child of sin" born when her mother, a saint, was defiled by the king of the Kingdom of Karman. She was exploited as a royal slave by her half-sister, Princess Isabella, and endured daily abuse. One day, Olivia is ordered by King Conrad to use her powers as a saint to assassinate the Archduke Alexis, feared as the "Ice Lion." Olivia is given secret orders to marry into the Principality of Blau, but Alexis, contrary to his fearsome nickname, showers Olivia with sweet love. Although Olivia is confused and distressed, she is drawn to the kind-hearted Alexis. What will become of this political marriage between the clumsy "Ice Lion" and the "child of sin" who harbors a secret...?