Juin no Onna Kenshi @comic

There was a time when mages were feared. In the Kingdom of Fulgund a female spellsword called Alfiris travels in the hope of becoming a "person who can save others." However, those who manipulate magic are shunned even by the mercenary guild. If one day she finds a travel companion and her "curse brand" is seen... One day she is reunited with Sister Anorn, a drunk who considers her a "friend," and gathers other companions to slay an archfiend. But when overwhelming despair strikes them, Alfiris's right arm bursts into flames and a different persona emerges!

(Source: TO Books, translated)