A former professional murderer known simply as R has been living peacefully for the last 7 years until he gets pulled into the life of a troubled teen.

Bong-Man used to be an accomplished hit-man but he gave it all up when he fell in love with one of his targets and married her. 7 years later, he lives a stunningly mundane life being bossed around by his now plastic surgery crazed wife and their teenage daughter. He yearns for his younger days when he was a strong and powerful killer but when an attractive teenage girl, Miu, enters his life, he suddenly finds a new reason to live.

Original webtoon (Korean webcomic)
http://cartoon.media.daum.net/webtoon/view/roman