It begins with toxic herbs placed beneath the cradle. Next, they are hidden under the sheets. Then, inside her clothing. They are even mixed into the milk used to feed the newborn. Through this process, the child gradually acquires immunity to poisons and is molded into the ideal assassination weapon—the "Poison Princess," whose every kiss, tear, and even touch brings death. Her sole chance of survival lies in fulfilling her duty as an assassin and finding a way to survive in the enemy territory to which she is sent... provided her heart is strong enough.