At the age of 30, Sia accidentally returned to her 16-year-old self, when she was a poor student at High School. Determined to make a comeback with her adult mindset, she got involved in two relationships. Jack, an outstanding student, approached her through part-time jobs and tutoring, confessing his feelings after a brief encounter. Rocky, a social youth, silently protected her. Everyone organized a get-together to form the "Nagai'er" band, and also dealt with the predicament of Rocky's ex-girlfriend and her friend's intentions. After being kidnapped, Sia and jack's relationship intensified. Rocky also demonstrated his responsibility. During a camping trip, the two unexpectedly kissed. jack's mother approved of Sia. And jack's chocolate mousse was exactly the same as the cake she had before her time-traveling. This left a mystery about the time-travel phenomenon.
