Fuka and Rinne stayed at the same orphanage during their childhood. After leaving the orphanage, Fuka works as a freelancer to earn her living.

One year before the story of ViVid Strike!, the friendship of Fuka and Rinne worsened after Fuka explained her pity for Lyra Caprice, a striker opponent knocked out and commented badly in a post-match interview by Rinne.

(Source: Nanoha Fandom Wiki)