"Understand for yourself that you are worthless. You are already obsolete."
Dion, the recovery wizard who was told so, was seriously injured by the hands of party members and left behind in the interior of the highest difficulty dungeon.
On the verge of running out of his life, he happens to encounter a dying dragon. Dion realized that he couldn't help him anymore, and he treated the dragon to live as a recovery wizard until the end. Then the dragon thanked him and even shared the power of the dragon. In addition, this dragon seems to have been a legendary god dragon class.
Dion escapes from the dungeon with his new companion, the Dragon, and restarts as an adventurer. He captures the difficult dungeons that stand in his way, and his abilities are recognized and he has all the strong men on his side.
This is a story about a recovery magician who leaves behind even the party he was in from a difficult situation and becomes the strongest adventurer in the world.
MTL synopsis from syosetu.