The errands

Hye-Seon is a 19 year old girl who moved to South Korea with her parents after living in America for her whole life. One day Hye-Seon goes out to run errands for her mom but accidentally bumps into Namjoon while running across the street. Soon enough he finds out that Hye-Seon goes to his college, then him and the rest of Bangtan slowly falls in love with her. But it all changes when Hye-Seons first love comes back from America to plan on marrying her.
Who will Hye-Seon fall in love with?