Wendy, a young lady from a wealthy family, lives her life freely. Throughout the years, her parents let her decide on her own and do whatever she wants. But because of an unexpected turn of events and an old promise, Wendy finds herself getting married to Kyungsoo - who happens to be her best friend's older brother with a grumpy attitude that she disliked when they were younger. What things can possibly happen if they settle under the same roof and become newlyweds?