Shin Woo Yeon is a handsome and intelligent professor. He is also a 999-year-old nine-tailed fox. To become human, he collects human energy in a pearl, and is almost on the verge of becoming human. Lee Dam is a college student. One day, an accident occurs that changes the fate of these two people. Shin Woo Yeon’s pearl falls into Lee Dam’s mouth, and she swallows it unintentionally. The pearl can remain inside a human body for only one year; after that, it will shatter, and Lee Dam will die while Shin Woo Yeon will lose his chance to become human. So the two find themselves living together until they can find a solution.