Dan Bi is a high school senior who has given up on math. On the day she is about to take the KSAT for college, she is transported back into the past during a freak rain shower. She finds herself hundreds of years in the past at the height of the Joseon Kingdom, which is suffering from a severe drought. She encounters King Lee Do who yearns to learn advanced mathematics and falls in love with him. This is a romance that transcends space and time with two lovers who come to know each other on a deeper level. (Source: MBC)