Mushoku Tensei: Jobless Reincarnation ~Eris Sharpens Her Fangs~

Eris Boreas Greyrat takes center stage in this spinoff from the wildly popular series, Jobless Reincarnation! After facing a devastating defeat at the hands of Dragon God Orsted at the Red Wyrm's Lower Jaw mountain range, Eris parts ways with Rudeus and makes her way to the Sword Sanctum in order to rectify her own inexperience as a swordsman. As the "Mad Dog" continues to hone her sword skills under the tutelage of the Sword God, her fangs continue to grow stronger and sharper!

(Source: Manga UP!)

This is a spinoff of Mushoku Tensei which splits off from the main manga at around chapter 51 (volume 6 of the light novel, first season of the anime).