One Step Away From Happiness

Binah has lost her father in an accident and ever since her mother worked hard to earn money for both of them. She often left alone at home while her mother was working. During that time, she met the twins Heeseo and Heewun and soon they became close friends, even closer as family.

A few years later, Heewun confessed his feelings to Binah. The thing is, they have the 10 years age gap. What would happen to their long friendship?