Unwanted Immortal Adventurer

Our hero, Rento, was a bronze-ranked adventurer in the frontier for many years. Unfortunately, he encountered a powerful monster deep in the labyrinth, was defeated, and found himself transformed into a skeleton. He was worried that he couldn't even enter the town, so he remembered the existence and evolution of monsters, and set out to defeat monsters in the labyrinth, aiming to obtain a body with flesh.