Kazuha hasn't appeared in the game yet. Accroding to the leaks, she is Anemo Sword user from Inazuma. We don't know any other about her now.
Here are 3D models shared by Lumie. Check the original tweet here.
Lumie
@lumie_lumie
image
Matangkad
@Woohyunyeah
@NEPTUNE_XVIII Hutao ans rosaria is the next one according to leaks
Zeniet
@Zeniiet
Males https://t.co/EjN8v0MyZx
Puzzles, Secrets, and Hidden Chests in Liyue
Kazuha
Mirror Breaker
Kamisato Art: Senho