The Unwanted Undead Adventurer v01-v03 (2019)

English translation of the Japanese manga Nozomanu Fushi no Boukensha (望まぬ不死の冒険者).
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 Labyrinth of the Moon's Reflection...and is summarily eaten. But Rentt has miraculously reawakened...as a Skeleton?!