After being dumped by her boyfriend just before their 100 day anniversary, Ha-Young, meets a college guy named Hyung-Joon when she accidentally kicks a can that hits him in the face and causes him to scratch his Lexus. He demands she pay him $3000 on the spot. She escapes from him, leaving her wallet behind.Hyung-Joon stalks her, demanding money to pay for his car. Since she is a poor high school student Hyung-Joon writes up a “Enslavement Agreement” for Ha-Young in order to pay for the damage to his car. Ha-Young is thrown into a nightmarish slave life for 100 days, cleaning his house, running his errands, doing his homework and cleaning his car.By accident she finds out that the damage to Hyung-Joon’s car only costs $10! She then takes her revenge. However, before she knows it Hyung-Joon shows up at her house as her new tutor! He once again takes advantage of her, but soon Ha-Young finds herself falling head over heels for Hyung-Joon.

Six years ago a mysterious shooting takes place in Seoul. The after effects of the shooting results in Han-kyu Lee (Song Kang-Ho) losing his job at the NIS (National Intelligence Service). Six years later, Ji-won Song (Kang Dong-Won), an ex North Korean spy. now operates somewhere in the Seoul metropolitan area. As these two men hide their identities and work their particular angles, trouble brews again ….