Synopsis: Only I Know About "Leveling Up" in This World

In a realm where one's life value is determined by their Level, Theo, an S-Rank adventurer, finds himself reincarnated a thousand years later in a time when the concept of "Level Up" has been forgotten. In this society, individuals start as Level 1 at birth, and humanity has become the most oppressed race, living in constant fear of monster threats. Yet, amidst this turmoil, only Theo, who was selected as a sacrifice for the monsters, is aware that humans have the potential to become the mightiest, as they alone possess the ability to Level Up.