A staircase leading to a schoolgirls' dormitory usually has 28 steps, but sometimes a 29th step appears. Any wish you make while standing on this step comes true, even if it must come true in the most horrific way possible.

Na-nan has known best pals Dong-mi and Jung-joon since childhood, and now the trio shares the ups and downs of their turbulent single lives together. But everything gets turned on end when Dong-mi and Jung-joon end up in bed!