The Unwanted Undead Adventurer (Manga) Volume 1

It's been ten years since Rentt Faina, a down-on-his-luck Bronze-class adventurer, set his eyes on becoming Mithril-class. Unfortunately, Rentt 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?!