Mushoku no Tensei – Eris Gaiden

Story:

Eris Boreas Greyrat is a noble girl who is transported to the other side of the world with her cousin Rudeus. She grows as a swordswoman, but ultimately fails to save Rudeus from being nearly killed. She decides that she wants to be someone who can support him rather than the other way around and so leaves him on his own journey. This is a spinoff of Mushoku Tensei, which splinters off from the main manga at around chapter 51 (volume 6 of the light novel, first season of the anime).