A washed-up adventurer dies pathetically and wakes up as a skeleton, which should be a joke premise. Instead, the show treats his slow crawl back to humanity like a genuine philosophical question: what do you owe yourself when you've already failed at everything. The character writing is sharp enough that watching a coward figure out how to be brave again, one small monster at a time, becomes the entire point. It moves slowly on purpose, but that patience pays off in moments where Rentt's bitterness cracks and he actually cares about something besides his own resurrection.

Rentt Faina has spent ten years as an adventurer with little talent for the job, earning a few coins a day hunting slimes and goblins. When he finds a seemingly undiscovered path in a labyrinth, he thinks his luck has finally turned. Instead, a legendary dragon waiting at its end swallows him whole. He wakes up as a skeleton. Rentt soon learns that slaying the labyrinth's monsters earns him experience toward higher stages of undead evolution, some of which even have flesh. His new goal is to keep evolving until he becomes a vampire, the highest undead form and one that can pass for human. Hiding his face behind a mask that will not come off, he returns to something like his old life. Lorraine Vivier, an elite researcher and retired adventurer, takes him in, and he starts over as a rookie under her surname. He still chases his childhood dream of reaching mithril class, but he has to keep his true nature secret, or the adventurers' guild may come to destroy the monster he has become.