Hindsight (2011)

Doo-Hun (Song Kang-Ho) is a retired gangster boss who confronts a mysterious woman named Se-Bin (Shin Se-Kyeong). Se-Bin is a 20 year old assassin sent to kill Doo-Hun. Things become more complicated when the retired mob boss and sexy assassin start to develop feelings for each other. —luraz isketambola