Nozomanu Fushi no Bôkensha

The Unwanted Undead Adventurer is a story about a seasoned adventurer named Rentt, who persisted in his line of work for a decade with rather modest progress. One day he discovers an unexplored passage in a labyrinth thought to be completely mapped. Frustrated at his slow progress he decides to take the risk of looking around for a bit before reporting to the guild. There a dragon-like creature devours his flesh leaving him an undead skeleton. That change, however, doesn't break him down. Thanks to his friendship with an eccentric alchemist, he is aware of monster's ability to advance through existential evolution. Hence Rentt decides to attempt returning his body as close back to human as possible. Soon he will discover that, besides obvious drawbacks, his recent form also provides new prospects towards achieving his dream - becoming a Mythril-class adventurer.

A pretty straightforward and common premise, but the implementation in this case is astounding! Just imagine the non-suicidal adventurers who don't delve headfirst into danger! The guild that actually manages its members! The trial where participants aren't left to roam or die randomly, but are actually both observed and tested! *(hello to Demon Slayer with its 20% survival rate)*

Now imagine all that coherence combined with likable characters, decent quests, and adequate world-building, and you will get a pretty good show. If it proves to have an interesting main storyline in future seasons it might even be great, or better. Looking forward to finding that out!