When Suyun loses her phone and her camera, a fatal accident triggers an encounter with the new neighbor, Yong Gook, who will soon be attending her school. Having a new "oppa" by her side (what with her original brother taken away) Suyun's once bright life will turn into a neverending hell when she stumbles upon a dark secret that she was never meant to discover.

Kim Suyun

A bubbly, happy-go-lucky girl with a charisma so charming that everyone is drawn to her. Her cute and kiddy persona is only one of her 4-D personalities, and it's the one that shows the most. Suyun is never seen without her trademark smile and she never seems to be sad. Her caring, warm heart is what lead to the footsteps in the shadows.

Bang Yong Gook

An outsider who has recently moved to Suyun and Jaekyo's neighborhood keeps up a harsh and distant image. With him he carries a kind heart yet everyone turns him away without a second glance. Suyun's pure smile and genuine compassion was what drew him to her. Undiluted intentions in mind, Yong Gook recovers Suyun's missing possessions. His mind and concentration become tainted, the purity in his kind heart overflowing, as he befriends Suyun.