The Unwanted Undead Adventurer Vol. 1 (manga)

It's been ten years since Rentt Faina, a luckless Bronze-class adventurer, set his eyes on becoming Mithril-class. Unfortunately, he finds himself helpless when confronted by a legendary dragon in the Water Moon Dungeon...and is summarily eaten. But Rentt has miraculously reawakened...as a skeleton?!Making his way back to civilization is going to be a challenge when he can barely walk, let alone hold a sword.

And the good people of Maalt won't take kindly to a monster in their midst. Can some magic techniques and a chance encounter provide Rentt's salvation?