It is said that the body contains heartstrings inside the heart that supports it. Sometimes when people go through heartache these heartstrings can rip and it is extremely painful. So when people are saying love is dangerous they aren’t really wrong. Mark soon learns this lesson when he falls in love with his best friend who is infatuated with a girl from school. Loving someone who doesn't love you back seriously . 

"Well," Jackson gives a short laugh, tapping the floor, "it's not just that. You've kind of been hanging with Yugyeom a lot. I mean, he went to the States with you."