Leon, a Class-D esper, was publicly cast out by the Shaw family after his "Awakening Day" assessment revealed his ability: "HP Doubled." In his moment of despair, a mysterious system granted him the power to alter a single character in his ability’s description. He changed "doubled" to "hundred-million-fold"—instantly gaining an HP pool in the tens of billions and total immunity to one-hit-kill effects. After severing all ties with his family, he ventured alone into the Valley of Villains, only to realize—amidst swarms of mutated beasts—that he was the true monster. He formed the "Undying Squad," conquered lethal dungeons, reached the 99th floor of the Tower of Heavens, and claimed an ancient legacy. When an allied coalition arrived, armed with holy swords and forbidden arts to hunt him down, he unleashed his 990 billion HP and a "Forbidden Domain of Life," crushing five hundred elite warriors with a single punch. In the end, he transformed the Valley of Villains into the "Valley of Rebirth," becoming a guardian for all those cast aside by the world.
