The Worst Guy Ever(2007)

Ju-eyon and Seong-tae have been best friends ever since they first met each other 10 years ago. But in one night their 10 year friendship comes crashing to the ground after they sleep together. The comfort and security of marriage is a siren call, and the two decide to forego their ideals to spend their first day as man and wife. However, their perfect lover soon appears right in front of them: A sexy editor appears to seduce Seong-tae and an advertising director appears to tempt Ju-yeon. With a single smile they turn the newlyweds dream into a nightmare. Even after only a few days, they soon find themselves faced with the worst choice of their lives as they struggle to reach happiness.