Gu Chang leads to a tragic existence. The seventh-year college student constantly fails job interviews and lives off of an allowance from his divorced sister while taking money from his little nephew. To make matters worse, the almost 30-year-old virgin has never had a girlfriend, let alone experienced his first kiss. In Korean, Gu Chang is a homonym for the word meaning "a sore in the mouth".
But springtime finally seems to have arrived for Gu Chang, defrosting the stark winters of his barren love life, when he meets the sweet and innocent Ah Ni.
All seems to be well, and Gu Chang gets a taste of heaven as he kisses his pretty girlfriend for the first time - until Ah Ni bites his tongue and gives him a nice kick, introducing herself as Ha Ni. And so begins Gu Chang's painful relationship with his split-personality girlfriend, dealing with Ah Ni's adorably childish demeanors one moment, then defending his life from Ha Ni's high kicks.