Kim Taeyeon and Tiffany Hwang used to be best friends until the Hwangs decided to leave for US. They stayed there for 4 years leaving the two with no communication at all.

After 4 years the Hwangs returned but Taeyeon welcomed a new and changed Tiffany. Her sweet and pure best friend came back as a bad and a huge pain in the head earning her the title as SM High's queen delinquent. Meanwhile Taeyeon stayed the same sweet and smart girl. She thinks of herself as a ‘nerd’ or she preferred the 'gifted one' but everyone knows the goddess she is behind those thick eyeglasses she insisted on wearing. Because of this the two best friends drifted apart. One being the troublemaker everyone tries to avoid while the other the sweet angel everyone loves. But one dark past from Taeyeon's life came back causing the Hwangs and Kim’s to make a move to protect Taeyeon.

How will the two react when they're forced to live under one roof, stay together at all times and even take the vow of marriage in the future? Will they hate it? Or will they actually love it?