New high-school transfer student Na-Mi comes from a small town in Jeolla Province to her new school in the capital city of Seoul. When she is nervous, her small town dialect comes out & she starts to shake. On her first day at her new school she is bullied by others. Coming to her help is a group of girls. The girls are Choon-Hwa - known for her strong sense of loyalty & excellent fighting skills, heavyset Jang-Mi - who badly wishes to have plastic surgery to get double eye-lids, Jin-Hee - excellent when it comes to spewing profanity, Geum-Ok - interested in literature, Bok-Hee - dreams of one day becoming Ms. Korea and Su-Ji - always arrogant. Na-Mi quickly becomes part of their group. When the group confronts rival girls known as Sonyeo Sidae ("Girls Generation"), Na-Mi spews curse words she picked up from her grandmother. Because of Na-Mi the girls are able to avoid a crisis. These seven girls then form their own group named "Sunny". They also vow to stay together forever. The girls then prepare for a performance at an upcoming school festival, but on the day of their performance a terrible event occurs leading the girls to eventually going their own separate ways. Twenty five years later, Na-Mi is married to a successful businessman and has a beautiful daughter. Her life seems perfect from afar, but there's something lacking in her life. One day, Na-Mi bumps into high school friend Choon-Hwa in the hospital. They are ecstatic to see each other, but Na-Mi receives a phone call and has to leave. On her way out she ask Choon-Hwa if there is anything she can do for her. Choon-Hwa at first says no, but after a moment of reflection she makes a simple request to Na-Mi. Choon-Hwa asks Na-Mi to find the other members of "Sunny," so she can see them one more time.