My Younger Brother’S Friends summary: After her parents died in an accident, Gaeun, a senior student in college, lived with her younger brother, a high school student. She lived brightly and confidently while hiding her pain. After breaking up with her boyfriend, who was her ideal type, she thought she wouldn't date anymore. However, she ended up getting tied up with Dowan, who knew her since they were young, Sangwoo, who was her younger brother's class Vice President, and Joon, who was a part-time student in an Art Academy. It suddenly became an ambiguous atmosphere amongst the younger men. One day, Gaeun gave an invitation to her friends saying that she'd decided to marry her younger brother's friend. Ultimately, which of the three will she marry…?