High growth scores in isekai often mask a fundamental distinction between genuine evolution and mere behavioral calibration. While both Rudeus (YPS-4) and Shalltear (YPS-3) share a Growth score of 80, they move in opposite directions. Rudeus fights the gravity of his previous life as a shut-in; his arc is an agonizing climb toward sincerity, moving from treating the world as a simulation to embracing the terrifying stakes of fatherhood and marriage. His progress is an expansion of the self. In contrast, Shalltear’s arc is a regression toward a pre-determined ideal. Her psychological shift after the mind-control incident is not an expansion of character, but a desperate attempt to erase the "glitch" of rebellion and return to the absolute submission dictated by her creator's settings. This is where the Ego gap—45 for Rudeus versus 15 for Shalltear—becomes the defining metric. Rudeus possesses enough self-determination to be terrified of his own nature, whereas Shalltear lacks the agency to desire a nature other than what her master expects. The comparison exposes a harsh truth about the genre's DNA: for a reincarnator, growth is the struggle to finally become a person, but for an NPC, growth is simply becoming a more efficient tool.