I'm a Middle-Aged Man Who Got My Adventurer License Revoked

Story:

Douglas was once known as the strongest legendary magician. But now he is called an old man and his body is gradually weakening. He is tormented by strange symptoms. The team of brave men falls apart, and in the end, the guild deprives him of his license as a guild of adventurers. After that, Douglas travels alone. During the wanderings he meets a damned girl named Ravi. How will their journey end?