Rentt Faina, a twenty-five-year-old adventurer, has been hacking away at monsters for a decade. However, without much talent for the job, Rentt finds himself stuck hunting Slimes and Goblins for meager amounts of coin every day. Little does he know, all this is about to change when he comes across a seemingly undiscovered path in the Labyrinth of the Moon's Reflection. What awaits him at the end of the path, however, is neither treasure nor riches, but a legendary dragon that wastes no time swallowing him whole! Waking up a short time later, Rentt finds himself not quite dead, but not very alive either— He is nothing more than a pile of bones! Armed with nothing but his trusty sword, tool belt, and ghoulish new looks, Rentt sets off on his quest as a newly reborn Skeleton to achieve Existential Evolution, hoping to one day return to civilization with a more human form. Will Rentt succeed, or will the labyrinth consume him for the rest of his un-death...?

With the help of Lorraine, Isaac, Laura, and the rest of his companions, Rentt defeats the vampire Shumini after he attacks Maalt. However, in order to take control of the new dungeon, Rentt has to turn Rina into a vampire and make her his familiar.Both Rentt and Rina have leveled up, so Isaac suggests they try out their newfound abilities. He also offers to teach them about a vampire's most notable skill: Division. Not everything goes as expected though, because while they were supposed to transform into a bat, Rina transforms into a cat and Rentt into a...tree?Meanwhile, people are flocking to Maalt to study the newly formed dungeon. Not to be left out, Rentt and his companions set out on their next adventure to explore the dungeon's secrets!Fighting powerful monsters, solving countless mysteries, and becoming stronger! The adventures of Rentt, the undead adventurer who aims to become a Mithril-class adventurer, continues in this thrilling ninth volume!