When Ha-mi (Han Ji-hye), a romantic believer in fate, meets Young-bin (Lee Dong-geon) by chance on the street, it is love at first sight. But the charming and handsome Young-bin has the blood type what all women dread or consider a nightmare, type B.

Ha-mi is head over heels for Young-bin, regardless of her cousin’s strong objections. Young-bin prepares various romantic events to capture Ha-mi’s heart, but Young-bin is only a college-boy turned businessman, with no home, and values his appearance more than anything else. In fact, he even resells the bouquet of flowers he gave Ha-mi as a gift, or buys gift coupons as gifts for Ha-mi. His typical type B stinginess bewilders Ha-mi. Though his idea of dating may be creative, some of them are too unique, such as sneaking into an empty office to do hurdles, or playing superman inside an elevator.

Young-bin becomes more ill humored and selfish as time goes by, forcing Ha-mi to break up with him. Young-bin realizes later that he was genuinely in love with Ha-mi and unsuccessfully tries to win her back. The type-A woman who does not look back once she had made a decision, and the type-B man trying to win her heart back creates the worse combination, and there is no turning back when Young-bin follows the advice of his friend Gyeong-jun.