Kyouran Reijou Nia Liston: Byoujaku Reijou ni Tensei shita Kamigoroshi no Bujin no Karei Naru Musouroku

A legendary warrior dies undefeated, regretting that she never found an opponent capable of bringing her down on the battlefield. Her soul does not disappear. Instead, it is placed inside Nia Liston, a frail noble girl dying from an incurable illness. The new Nia uses chi to attack the sickness at its roots and begins rebuilding a body far too weak for the restless fighter now living inside it. She has received a second life, but her desire has not changed: travel, fight, and find the person who can finally defeat her. The only problem is that the body of a young noble lady is not an especially convenient place for that kind of ambition.