Presuming the question is about "Roshin Yukai" (Nuclear reactor) sung by Vocaloid Kagamine Rin.
There is no definition to what the song, PV, its characters or story means. It is left to interpretation. The most popular theory is a song of a sinful woman trying to forget her past by suicide (in a symbolic sense); another is a woman who overcomes her past doings and continues to live her life.
- See also