The Late-Blooming Explorer

It's been 10 years since Ignis became an adventurer, yearning to be a hero. Feeling he has hit a wall in his career, he considers retirement. But when his life is saved by an elf slave girl who has been blessed with a mysterious power that prevents her from dying he decides to buy her using the last of his savings, and a new life for the two of them begins.

(Source: Amazia)