VIVID STRIKE!

Raised up in the same orphanage, Fuuka and Rinne were once close friends but parted ways after a quarrel ended up with Rinne overwhelming Fuuka with her martial art skills. Fuuka lived a life of poverty after leaving the orphanage but an accidental encounter with renowned martial arts champion Einhard Stratos leads to the discovery of Fuuka's hidden talent in fighting. Einhard offers Fuuka a job and through her coaching and encouragement, she is set to meet Rinne again, in the ring. — Description from AniList community (anilist.co).