Read manga: The Little Girl Raised By Death Hold The Sword Of Death Tight

manga
Summary:

Olivia is picked up by a death god, Z, deep in the forest as a child and trained by him in combat for reasons unknown. One day, Z disappears, leaving behind a letter instructing Olivia to head to the Kingdom along with a sword bearing the qualities of a death god's weapon. Thus, the girl lacking in common sense, knowledge, and normalcy sets off to join the army.