After 15 years of marriage, things just weren't the same anymore. The love and attraction was slowly drifting apart. Old habits came back and parenthood soon became a bond between a parent and child only—not a partnership. When they laid eyes with each other, there wasn't a spark anymore; instead there was a glare. Angry words became louder which erupts into a heated argument. 

After 15 years, Do Kyungsoo and Hwang Minrin had hit a plateau in their transient marriage. 

This is a spinoff to Boundaries of the Heart but regarding Kyungsoo and Minrin's marriage life.