The series takes place four years after the events of Magical Girl Lyrical Nanoha StrikerS, during which magical girl Nanoha Takamachi rescued and adopted a young girl named Vivio, who is the reincarnation of the Sankt Kaiser, Olivie Segbrecht.
The spin-off series, ViVid Strike!, focuses on an orphaned girl named Fuuka Reventon who was defeated by her former friend, Rinne Berlinetta.