Boukensha License wo Hakudatsu Sareta Ossan Dakedo, Manamusume ga Dekita no de Nonbiri Jinsei

Douglas Ford is a mage who has spent the past two decades using his magic to help others, ever since he became an adventurer at the age of fifteen. Now thirty-seven years old, he's contracted a mysterious ailment that causes his HP to drop whenever he uses his powers and his body is starting to wear out. When his guild unceremoniously kicks him out after his adventurer's license is revoked, Douglas wanders the land alone and encounters a little girl who has been transformed into a giant wolf. He decides to use up the rest of his dwindling life force to change the child back, but when casting the spell doesn't actually succeed in killing him, Douglas finds himself with a brand-new purpose in life - raising his new daughter!